VPN does not disable SBMM. It only connects you to servers closest to the country your VPN is set to.
If you are in Asia (PH,SG,MY,ID,CN), lobbies are either extremely sweaty or full of cheaters even in easy lobbies. So using VPN to connect to like other regions will probably get you easier lobby/rare any cheaters however the tradeoff is you have to deal with 200-250ms ping.
I know this because I have friends in USA so being in asia, ill join their lobby and connect to USA and its totally different. I rare come across any cheaters and players are more casual but I have to deal with high ping