I owned a Otari 5050blll which I loved after owning revoxb77 teac4010 and a few others throughout the years
and can say the Otari will sound better but the real difference would be in tape handling compared to consumer decks, it is very gentle and first class which is important when your spending big money for tapes.
If it functions properly you may get more bang for your buck by wiring the heads direct out to a tape pre instead of rebuilding the inner electronics, but its your choice. I enjoyed the Otari but sold it and currently use a Sony APP5003.
As far as tapes go the current tapes being produced sound like nothing else, Tape Project,Acousic Sounds,Music Direct all sell great sounding first class packaged tapes one of my favorites is https://www.internationalphonographinc.com/master-tape-copies/
they sell at reasonable prices and will get your collection going fast, and they sound great.
My 2 cents