Obviously 2 of the same camera is best but is it a lot of trouble For a 2 camera shoot to match an FS700R with FS7 (or FS5)
1 internal 1080P
2. and also internal 4k FS7 and external recorder FS700R ?
They are remarkably easy to match. I suggest shooting Slog 2 or RAW to external recorders, they should be as close as two cameras can reasonably be. Grab a color checker if you're the type who agonizes over a 10 degree Kelvin shift.