I run Merlin firmware on the Asus .. it supports PPTP server as well as OpenVPN.
But I think it is now included in the latest Asus firmware as well.. since Merlin acts as a beta development.
I have not had need to run VPN from iOS devices.. so my experience there is certainly lacking. But your post specifically mentioned no PPTP.. so for cheap routers that support something else.. you are going to be struggling.
works with IOS 11 and higher (no PPTP)
Sorry I have nothing with iOS 11 capability. So not in a position to test. I can beg my son to loan me his iphone.. but I sort of doubt he will.. 😁
If you want L2TP server in a router.. you are after something business class. The only way to get that is go for something second hand.. business routers come off lease and I have picked them up very cheap.. but it is hard to find on the day and you need to be patient.
Or go for Mikrotik or Ubiquiti .. but you will need to learn the router OS.
The edge routers are very reasonably priced.
What kind of actual VPN throughput are you looking for??
BTW neither of those suggestions meets all your criteria.. because you want good wireless as well.. This is where I had trouble finding anything that came even close.. when you set a budget of $140.
You need to use a cheap WAP alongside any sort of router that you are likely to pick up for that price.