poll should have 7.3 version. I'm using 7.3.1 at the moment.
It depends on what I have to run unfortunately. 7.1 for Magento2, I have an old stack for an old site with tons of legacy software which isn't worth remaking at this time and it requires php 5. For wordpress I can get away with the latest php version usually.
IPS 4.4 that will be released next month, will drop support for PHP 5.6 and PHP 7.0. PHP 7.1 will be the minimum now. Main reason is because they are EOL and also because they want to start to use the new fancy things. Also, the main focus of IPS 4.4 is performance. Making the loading times as fast as possible. Xenforo is doing the same thing or they still use the old PHP 5.x?
XenForo 2.1.0 Release Candidate 2 & Add-ons Released (Unsupported) PHP 5.6 or newer (PHP 7.2 recommended)
It need to be 2 installations on the same server, but ips 4.4 is not released yet. At least for ips, it needs to be properly configured, since most cache configurations comes disabled by default, because they need redis, etc etc. An example, if i enter invision site as a guest (they are using ips 4.4 beta), the TCP Request only takes 42 ms. Full page loads in less than half a second. Logged in, the TCP request will go to about 350ms. PS: They admitted they don't optimize their server like we do with centminmod Basically they use default options for maximum stability. It could be a lot faster faster.