Big subject and appreciate what you're attempting to do (only taking "a moment" to discuss), but there's just not much info here. As a starter, highly recommend John Scrip's excellent article at Massive Mastering, link:
http://www.massivemastering.com/blog/index_files/Proper_Audio_Recording_Levels.php
John's blog explains the why's and some of the how's. Sound on Sound has a good introductory article at
https://www.soundonsound.com/sound-advice/q-how-much-headroom-should-i-leave-24-bit-recording
Many newbies don't understand that you (generally) can't control input recording levels from the DAW, although there are some apps which attempt to do this, e.g., MixCraft. Many of us have created our own recording input level guides for our USB interfaces, hardware mixers, or amps, so we know where to put the knob or fader for a good starting level. [as an aside, if you're using loops in your mix (commercial or otherwise) you're likely to find that they've been rendered at various volumes, and so you'll have to adjust them during the mixing process - point being that one size doesn't fit all when you're importing media items into your mix - whole other subject.] Also, your instrument may or may not have it's own pre-amp, such as electronic keyboards, mics, guitars, etc., so it's advisable to run those outputs through a mixer where you can control the level separately for each instrument - I use a
Mackie Mix12FX for this in my home studio. Everybody's gear suite is different and you have to get to know it, play with it, and set up rules of thumb that work for you in your DAW.
