All I play is the guitar so I wouldn’t even have a guess on how to do vocals.
Things have gotten a WHOLE lot easier!
I’ll explain if you wanna give it a crack.
Get a vocal stem of the song using https://ezstems.com/
Following these instructions on how to setup the vox to midi plugin (JS: IX/MIDI Tool II) in reaper. https://forum.cockos.com/showthread.php?t=147109
Find the key of your song with google or upload the song to https://www.audiokeychain.com/ (it also finds an average tempo)
Then when you are ready to play the song in reaper and have it record notes to the midi, open the plug in (ReaTune) in the vocal stem and choose the proper key on the “correction” tab.
Make sure it doesn’t change if you close the plugin (I keep it open so that wont happen.)
Once that process is done, go the vocals midi. Highlight & erase all the garbage notes. Join or split tubes (highlight and hit J or put red marker over note and hit S to split)
Click on a note to highlight it, hit L so it goes to the front, then add the text event and change the drop down from text event to lyric so it stays attached to the note. When you highlight the notes, if the text event doesn’t highlight it means they are not aligned properly. Follow the rules of about lyrics from vocal authoring about syllables and +’s and..
Viola, that’s about it. Technology did the hard part and you do the grunt work.