I have not done the regulator swap on my Betz board yet. But the reference devkit board uses 3.3V, and the datasheets are all fine about it.

The Betz board does some funky stuff to get their +5V USB input shifted down to 2.5V for powering the logic. It looks to me that there ought to be no issue changing the regulator for 3.3V, but if I were you I'd experiment more on the semi-fried board first, and maybe compare temperatures with the semi-fried devkit board you also have.

The PDF datasheet for the WT32i is required reading if you want to go for the bare module. It shows exactly what is needed.

Cheers