Hey, welcome back! Gear-wise, the 72.5 on your MTB and the 74.6 on your proposed FG compare well, but it would be interesting to compare the crank lengths on the two. FGs often use 165mm cranks, and MTBs generally use longer cranks. If you look at the inboard side of your cranks, it should have a marking like "170" or "175". If you could find that out, we could use gain ratios to compare the overall leverage.

That said, the approach I've taken is just to buy a handful of cogs and inexpensive chainrings,and then let my riding tell me which gearing works best.