I’m not sure what the Tor Project advice is these days, but my phone is setup to have Netguard hijack the VPN option of AOS and force select apps over tor (to Orbot). It’s annoying because in fact it is impossible for me to run Netguard and Tor over a VPN. Because Netguard hijacks the VPN, I cannot use a real VPN. I can run a VPN (generally openVPN), but then I must give up Tor if I do that. Orbot can only run in parallel, but because Netguard loses the VPN slot I can only use Tor-aware apps in that situation. So ultimately what you’re thinking is not possible with my tool chain (of old versions).