Honestly this is first ive heard about vrm debates with Ryzen. Looking into it there's quite the decision to make it seems. Whether itll make a huge impact im not sure of the extent. Difference it seems on how many phases the motherboard has and which CPU. 2600x would be fine on a B450 board and x470 recommended for 2700. It also seems b450 vrm quality mosfets are also found on x470 boards as well and there's talk of itx boards designed for smaller cases having higher quality mosfets to handle more heat.
https://www.reddit.com/r/Amd/comments/931uto/b450_or_x470_for_2700/
Imo i think its all blown out of proportion. If you have decent air flow migjt not be such an issue.
If you're worried get an x470 itx board