DrailJust buy boots that have changeable sole plates if you can't afford two sets of boots.
In terms of "safety" this is the best option and the reason why 99% of the boot manufacturers still do this.
Alpine ISO 5355 and Touring ISO 9523 are mutually exclusive from the TÜV's (3rd party safety tester) point of view. That means if you have a boot in the Touring ISO, it will not safely fit (despite it looking like it does) into an alpine specific binding.
This is why swappable norm grip pads (like what's on our Waymaker Carbon series) exist. They allow the user to have one boot that safely works with both binding types.
The other thing to consider is a binding that accepts the different boot norms, such as the Warden binding. But here you have to adjust the toe and release values if you are switching from dedicated alpine boot to dedicated touring boot. Or if you bought a boot like the Scarpa Maestrale and only want to use that one boot, you can use it in a pin binding and the Warden (once it is properly adjusted for that boot).