VIP Type decision

MaxMedov It seems like the better purposed device for the first layer would be a GTM or another device that can perform GSLB since it is going to be performing generic forwarding to a pool of VIPs anyway. Having a VIP to balance to VIPs adds unnecessary delay when the only purpose is to send you to multiple destination VIPs.

The VS type to choose is not obvious because it depends on several factors. Generally speaking:

• Performance L4 is used to forward traffic as fast as possible and the cost is you loose many advanced functionalities which are available on the standard VS.
• Standard VS is the VS to go to take advantage of all the functionalities that the VS can offer, particularly Layer 7 manipulation and optimization. Since you go up to L7, the cost is most processing and time needed to serve traffic.
• Peformance HTTP is a type that is used to increase performance for some types of HTTP traffic, it is only relevant when the traffic condtions are optimal, thus it is most likely not efficient for internet facing traffic.

With that being said, there are many factors that will let you choose one or another, and using Performance L4 does not guarantee that the overall performance will be better: for example the Compression and Acceleration (cache) profiles that are available on the standard type (and not on the L4) can make the overall user experience better than with L4 VS.

On another side, using L4 or performance HTTP VS does not let you associate a WAF policy to the VS, so your backend VS both need to be on an F5 that has the WAF license.

So I think you should conduct a global approach (including the GTM option) to decide what to use. Or just test all the possible types and compare the results.