Why do you say they are the only provider to offer clean client? That is a big claim isn’t it!
StreamVia, which I use, offers a client that is light, clean and accessible. You can choose to connect to their various servers, which are located in different geographical locations. They quite good for streaming media; I always use their VPN to watch BBC iPlayer when travelling for example. They do offer a special sort of connection to cope with streaming videos but I have never had to use it. I found their London based customer service helpful in the one occasion when I needed help. I pay £3.99 a month and that gives me access to the UK servers. I believe it is £4.99 a month to have access to all their different geographical servers. Among other countries, I used their VPN on a work trip to China and it worked perfectly. And yes, their client works on Windows and iOS and I am sure it works on Android too.