Have you ever tried a Windows Phone before? As in use anybody else's phone for a while just to check it out? If not then you should do that first, cause even though WP is a great platform, some people just don't like it, so you might want to check it to see if it suits you or not.
If you're bored of using Androids, then you're most likely good to go for WP though, you will find it refreshing.
Resale value is a bit of a problem for these Lumias in Pakistan though... but if you're the type who keeps a phone for long periods of time then it won't be much of an issue for you.
I've checked the specs of Lumia 730, it seems like a good purchase to me. I would say you'd be good to go for it.
Also, if you don't mind buying a phablet, then Lumia 1320 is also a good option in your budget.
I would advise against buying any Huawei phone, they're simply not worth it. Also, the Honor 3C or G700 in particular have no redeeming qualities. So a big no from me.
And no, an end user cannot delete the Windows in a Windows Phone. In fact, Windows Phones are much harder to f*** up than a rooted Android phone...
Any other question, shoot!