I do not understand properly, what your topology is. 4 different routers TL-R470T+? Or 4 WANs on 1 TL-R470T+? 4 other routers, which are connected to 4 WANs of TL-R470T+?How is it connected in balanced mode?

Anyway, firstly there is a question, why you need the same IP. If you need it for some websites/hosts, then you can just configure Policy Routing, so for specific IP-addresses you will use only specific WAN. Usually, option "Enable Application Optimized Routing" works fine and hold the WAN for Application it uses first. Otherwise, such behaviour is totally OK, as you use 4 different WANs/4 different source IPs. 

i have 4x wans on 1x r470t+

load balance mode i left both options unchecked :

Hi beardhunter

As you said, I think a application would use only one wan if you had checked the "enable Application optimized routing".

And when you set up the VPN, you need to choose the WAN interface. So VPN will only use one WAN. And VPN will encrypte the packets, it will take up the source so VPN throughput is less than NAT throughput.

VPN will use only 1 WAN, that's true, because it is a point-to-point tunnel. Moreover, VPN will lower your speed, because of encryption. Usually, you can see maximum throughput on specificatios. Yeah, speed will be good for some multiple destination things, such as torrents (where you have a lot of seeds), while point-to-point connection (for example, you just download something from some FTP-server) will be as 1 WAN speed.