Plus and minus points on hosting your own VPN. For one, only you and possibly you and members of your immediate circle will be using it at it will have a fixed IP address. So websites, etc. can use that for some tracking purposes.
In addition, any server you run will need to be maintained which takes some effort and usually some money.
If your Nextcloud is hosted at your home then you want a way to get into your house. See if your router supports VPN server functions. I think many routers do nowadays including some open source variants.
My router can function as a VPN server and I use that to access my home servers. That might work for you. Free and not a lot of additional maintenance as I need to keep my router up to date anyway.
But if I wanted to hide things from my ISP, it turns out my router can also run a VPN client and has rules about what traffic goes over the VPN that I can customize. So, in a case like I think you have, the router could provide a server for home access and then all traffic out from the house (including from the incoming VPN) can be directed out over a different VPN to a provider of my choice.
I think my last choice would be to setup a VPN server on a VPS. That costs money and maintenance effort. And it won’t really hide my IP from tracking sites as I wouldn’t be “lost in the crowd” as my household would be the only ones on it.