Wongwian (Yai) was just ok when I lived in the area (Lived Pinkloa and Bangwa). Since I moved away I understand they've added a couple of trains otherwise it has sucky traffic. Silom has a nice charm.
I think Bangkok is an awesome city and a lot of fun... However, found the lack of Engish to make things more challenging. I now live outside of Pattaya and English is pretty common. Have you thought about other areas outside of Bangkok?
travel router - I think you mean mobile hotspot, use wifi for internet access across several devices?
VPN - encrypt connection between two computers (routers, etc). Used often to hide your current location.
I think you want the mobile hotspot. If you are using a US phone than you will want one of these. Or, buy a cheap phone - does the same thing but then you have an international phone. Mobile wifi will get you better quality internet probably.
I have been a tourist for about 9 years. Sure it's strange but not uncommon. Truthfully, I have used various different visa types over the past 9 year but most were tourist.
METV is a better option. Then you only have to do border bounce (go have lunch in a neighboring country).