Question for Tom CZ3D, F70 and F75LTD

Using F70 or F75LTD in 3H tone will this be like using CZ3D in enhanced mode bringing all coins to ring as high tone?

No. You must invoke 4H-tone...... to have nearly identical 'old coins' tone ID like the CZ-3D......... with one additional set of instructions:
You must dig/recover the TOP 2 TONES in order to achieve CZ-3D intent.

Maybe I should also use my CZ3D for certain places?

I run the F75SE in 4h for that very purpose. I had a CZ3D and loved it. The F75 is much faster but (in my opinion, of course) the CZ is much easier on the ears.... I will definitely own another. Use the CZ at older sites...