I have customers that want to use StrongVPN or PrivateInternetAccess or HideMyAss for streaming TV from the USA.

Security is not the number one priority but speed is a priority.

And does anyone have the proper settings too.

I have been able to handshake with PrivateInternetAccess.com but speeds are near ZERO. On the other hand when I use a Linux or Windows PC VPN cliet (PPTP), speeds are 30 mbits or more. Can't seem to get any support out of these providers for MikroTik.

Is there an issue/bug with adding a PPP interface? It seems that when I do it automatically adds a 10.x.x.x gateway and route. I would prefer to specify the gateway and route explicitly.

As an alternative may I suggest you getting a Linux VPS box instead if you need only one location? That way you'll have your own dedicated IP and your own VPN server software config, you can adapt to use with Mikrotik. And it will be much cheaper. You can get a lowend VPS (more than enough for VPN) for something like $5-10/year with at least 100GB monthly transfer included.
Of course it involves installing & configuring VPN server software yourself, but there are a lot of step-by-step guides around and once setup you won't need to touch it anymore.

Any interface with an address will have at least one route, if you get a default route (0.0.0.0/0) you just need to uncheck ' Add default route'. I don't know of any particular problems with PPTP in 5.26 (but on the other hand I don't use it myself), but a potential problem could be MTU, try lovering it.

What about mangle rules for change MSS ? I don't have any. Is that a problem?

I like the suggestion of setting up a VPS. But could I run the VPN client on a Linux box here in my office and also run squid to proxy to the VPN ?