The easiest way would be doing it through commands that are automatically executed when the router boots.
First of all you need to know how to and where to put the commands so they would be executed every time your routers starts:
There's a file in /etc directory named rc.local, there you will be able to put any commands and they will be executed once your router reboots.
To edit the file use WinSCP software or vi command in CLI: https://www.cs.colostate.edu/helpdocs/vi.html
Once you're editing the file, you will need these commands in it by the exact order:
tar -C / -xzf /etc/profiles/
uci set profiles.general.profile=[profile]
(IMPORTANT, you need to enter your profile name here, instead of [profile], use 'yourprofilename')
And that's it, save rc.local file and try to restart your router.
P.S, you could use User Scripts page to insert commands too without editing rc.local and they will be executed on start, but you must fill out User Scripts for both profiles if you want them to switch between every time you restart the device.