I use the Aqua Clear Filter which has a knob to move from left to right to control the flow. On the lowest setting it barely disturbs the water and still does a great job cleaning the tank. Also, I keep the water level in the tank as high as possible so the water doesn't have far to fall from the filter and this reduces the amount of splashing.
I think all Bettas are different. Some don't like their water moving at all and some love it.* My first Betta Phlox loves moving water! He likes his filter turned up high and he often plays underneath it, letting himself swirl around in the current and then racing off, turning around and diving right back in. He'll do this for hours.* He also loves the airstone. I turn it on for about 20 minutes a day and he plays in it. He loves the feeling of bubbles all over him. He has great fun chasing the temporary bubbles at the surface made by the airstone. He looks upset with me when I come to turn it off, like I'm taking a favorite toy away!*

I'm installing a gang valve on the air stone today so I can leave it on all the time and control the air flow.
I wouldn't worry about your fish not building a bubble nest anymore. Phlox has never made one and he's perfectly happy. Maybe now that Fiction is in a bigger tank he's too busy exploring to make a bubble nest. As long as he's swimming and exploring he's happy.