My only advice is test on a hidden area the varnish/ stain combinations for the floor before you go for it. I'd even do a section and live with it a day or so. We did the same and stripped it all back, then put a light oak stain on and then began with two coats of varnish for durability, the next day I got the stripper bank as the top coats of varnish had significantly changed the colour. What followed was about 5 test attempts to get agood combination and we've solved it by putting in a brand new oak floor! FFS!
I thought I knew better... I've stripped and stained, or varnished a few floors and never quite had this problem before. I think it's cos this room has large windows front and back, back is south facing, so through the day the light changes considerably as does the colour. I never thought it mattered until now, but at one point we had a tango floor despite testing! Arrghhh ... Good luck!
Watch out for the difference oil or water based combinations can give and test test test!
Enjoy!