I also have a PSR-E443, and started to compose a reply last night, but needed to verify some things first to be sure.
First of all, the Master Volume dial and the Master EQ function setting have no effect on the sound when you're recording a User Song with the keyboard's built-in Song Sequencer, because the User Song is a MIDI recording, and the Master Volume and Master EQ have no effect on the MIDI data (i.e., changing them doesn't generate any MIDI events, nor do their settings affect any MIDI events that do get recorded). They strictly affect the audio output that's generated by the keyboard, so they have an impact when you record the keyboard's audio output, but not when you make a MIDI recording. In fact, you could turn the Master Volume all the way down so that no sound can be heard, and still record a User Song-- when you play back the User Song afterward, you can turn the Master Volume back up to hear what you recorded.
Gary already gave you good advice about the Master Volume, and I'll come back to the Master EQ in a moment.
The other settings you asked about-- Style Volume and Voice Volume-- do affect the volume of the User Song, but they're a little complicated, because the volume of each part (or channel) in a MIDI recording is controlled by three factors: the channel volume, the velocity of each note played, and the inherent volume of the samples (i.e., sound waves) that the keyboard uses to play the selected voice. Furthermore, the Style Volume actually affects all eight of the style channels, and there is not one but three Voice Volume functions: the Main Voice Volume, the Dual Voice Volume, and the Split Voice Volume. And finally, the Touch Sensitivity function will also have an impact on the volume of the MIDI recording.
Under normal conditions, the Style Volume and Voice Volume do not affect the Note On velocities. Instead, they affect the Channel Volume settings. However, if you turn off the Touch Sensitivity then the Note On velocities will be set to whatever the Channel Volume is set to for a particular part-- e.g., if you turn off Touch Sensitivity and have the Main Voice Volume set to 100, the Dual Voice Volume set to 80, and the Split Voice Volume set to 60, then the Note On velocities will be 100 for the Main Voice, 80 for the Dual Voice, and 60 for the Split Voice, regardless of how hard (fast) or how soft (slow) the keys are being struck. In most cases you'll want to leave the Touch Sensitivity turned on to one of the three settings so you can play expressively.
You can't do anything about the inherent volume of the samples used for each voice, but you can use the three Voice Volume functions to adjust the volume of each of the three voices (Main, Dual, and Split). Actually, you can't record the Split Voice in a User Song, so if you're using the built-in Song Sequencer to record then you can just ignore the Split Voice Volume. And if you aren't layering two voices together then you can also ignore the Dual Voice Volume. In any case, you should adjust the Voice Volume so the voices you're using sound as loud or as quiet (relative to the entire mix) as you want them to.
By the way, if you're layering two voices together, or are recording multiple tracks in your User Song, you might want to adjust the Voice Pan settings (Main Voice Pan and Dual Voice Pan) to help create more separation between each voice and track in the overall mix.
As for the Style Volume, it's a bit more complicated and mysterious. Each part (channel) of a style has its own Channel Volume setting, and the more sophisticated PSR-S and Tyros arrangers have a mixer display that let the user control each channel's volume, but the PSR-E models have a Style Volume function that modifies the style's eight Channel Volume settings as a whole. For instance, when I choose Style 001 and set the Style Volume to 127 (the maximum setting), the eight parts of the style have the following Channel Volume settings:
Channel 09 -- Channel Volume 046
Channel 10 -- Channel Volume 084
Channel 11 -- Channel Volume 079
Channel 12 -- Channel Volume 068
Channel 13 -- Channel Volume 077
Channel 14 -- Channel Volume 076
Channel 15 -- Channel Volume 127
Channel 16 -- Channel Volume 127
If I reduce the Style Volume to 64 (about 50.4% of 127), the Channel Volume settings are as follows:
Channel 09 -- Channel Volume 026 (about 56.5% of 046)
Channel 10 -- Channel Volume 048 (about 57.1% of 084)
Channel 11 -- Channel Volume 045 (about 57.0% of 079)
Channel 12 -- Channel Volume 039 (about 57.4% of 068)
Channel 13 -- Channel Volume 044 (about 57.1% of 077)
Channel 14 -- Channel Volume 043 (about 56.6% of 076)
Channel 15 -- Channel Volume 092 (about 72.4% of 127)
Channel 16 -- Channel Volume 092 (about 72.4% of 127)
So the Style Volume seems to operate sort of like a percentage setting, but not exactly.
Anyway, you can use the Style Volume to adjust the overall balance of the style's parts (channels) in relation to the Main Voice and Dual Voice.
Once you've got the volumes of the voices and style balanced the way you want, and have made your User Song recording, you can use the Master EQ and Master Volume to control the levels of the audio output for recording on your computer. I'm not sure how many bands the equalizer has-- three at the very least (low, middle, and high)-- but unlike the PSR-S and Tyros arrangers where you can adjust each band separately, the PSR-E has only some presets that you can choose between. And I'm also not sure how each Master EQ preset affects each band of the equalizer-- i.e., which band is boosted (and by how much) and which band is reduced (and by how much), or whether the bands that aren't boosted are simply set to a median level rather than reduced in level, etc. The best approach might be to record the audio output of the User Song once for each Master EQ preset, then listen carefully to the recordings to compare them and decide which one you like the best. It's probably going to be different for each User Song, because it will depend on which voices you've used and whether you want to bring out the low, middle, or high frequencies in the mix.
By the way, so far I've completely ignored some of the other settings that you might want to adjust-- Reverb Type, Chorus Type, Main Voice Reverb Depth, Main Voice Chorus Depth, Dual Voice Reverb Depth, and Dual Voice Chorus Depth, as well as the Main Voice Filter Cutoff, Main Voice Filter Resonance, Dual Voice Filter Cutoff, and Dual Voice Filter Resonance. In particular, the Filter Cutoff can help you change how "bright" or "dark" the voice sounds, by adjusting the frequency at which the voice's harmonics are cut off, and the Filter Resonance lets you control how pronounced that effect is. So you might want to experiment with adjusting the Cutoff and Resonance before you actually record the User Song (since they do get recorded in the song's MIDI data), to help you accentuate certain frequencies in conjunction with using the Master EQ for that.
The bottom line is that there's no magic formula or group of settings that will always give the best results, since each song needs to be approached on an individual basis according to the voices chosen and what you're trying to achieve.