I can't comment about rams but your betta should be fine with apistos, mine have never come to blows. There was some initial interest from the bettas, like 'what the F is that'
after the male squared off (flaring), there hasn't been any issue since.
Apistos are bottom dwellers, bettas top to middle dwellers, so they both have their territories. Just make sure you have some hiding places on the lower level/bottom of the tank. You can used roof slates, terracotta plant pots (small ones and make a small entrance/door way or even a hole on the bottom of the pot,
Apistos don't need a big hole to get through, i would say 1 - 2cms would be sufficient
Think about food too, I have 2 diff kinds of pellets, betta ones that float on the surface and sinking pellets. I find that my apistos will occasionally come middle level for food but prefer to stay lower.
They are shy fish and slowly build up confidence to emerge, so don't worry if you barely see them for a few days.
This is all personal experience though
