If I update will the phone work as normal after o rwill i have to do some technical side install thing?
updates in the same Android version (a15) are just that, regular updates you can do without disruption. For going to the next higher major version (a16) in a few months or a year, Murena usually waits with enabling those until they did some testing. It should go without disruption too then. Sideloading is a method to circumvent that wait and upgrade sooner.
However, on the security page it states it’s not encrypted.
With encryption only one thing matters: who has the keys. And if you don’t have them, any encryption matters in other ways (at rest, in transport), but not for a warrant. What you see in the webinterface on murena.io isn’t encrypted in a form that matters for a warrant.
murena introduced a sub-product called “murena vault”. Therein you really do have the keys on your side, but it isn’t that vault you sync the phone data to: emails, files, photos - that is outside the vault.