The Numark USB TTs tend to have very light platters - The ION I bought had good electronics but the platter was so flimsy and light that I got very noticeable wow&flutter - so I junked it and in its stead I resurrected my trusty old Technics TT with its SME 3009 arm and gave it a good home service - and bought it a new cartridge. I also bought an ARTcessories phono preamp and an external USB soundcard (Edirol UA-1EX - no longer manufactured) and both of those have gain controls. If I was buying today I would buy the ART device that combines phono preamp with USB output: http://artproaudio.com/turntable_preamps/product/usb_phono_plus-ps/
So if you are going to stick with the Numark I think that will be your limiting factor as to quality. I would suggest working with Audacity set with its default quality settings 32-bit float 44,000 Hz and when you export the final result export to the default WAV 16-bit PCM stereo 44,000 Hz (CD quality as per Red Book standard) with your dither settting at the default “shaped”.
If you want higher quality there are better USB TTs around - but they do cost a fair bit more than the Numark.
Audacity is excellent for most of the LP transcription process but on extra tool I used when I transcribed mine (including classical) is Brian Davies’ excellent ClickRepair it costs a little but is well worth it if you have more than a few LPs. I had LP recordings of Joshua Rifkin playing Scott Joplin rags that I had given up playing on the TT/hi-fi as it was just too clicky - ClickRepair produced an almost magical result when processing it. See this sticky thread: https://forum.audacityteam.org/t/click-pop-removal-clickrepair-software/1933/1
WC