So, okay. Now it’s all becoming more or less clear.
At first. Regarding the configuration of Wireguard VPN clients in “RoadWarrior” mode. In my opinion, I have demonstrated the easiest way to configure this mode in this post.
The second. Regarding configuring a “Site to Site” VPN. In this case, a lot depends on whether there are static IP addresses on both routers that you want to connect in this way.
If both routers have static IP addresses, there are several VPN scenarios available to you for interconnecting them. The most common option that I use for this scenario is to create IPIP+IPSec tunnels. Well, or the GRE+IPSec variant. Although there is nothing stopping you from using any other variant for this.
In case, if only one of the routers has a static IP address, you will have to use something like L2TP+IPSec. Which, in fact, is also a good alternative and makes a lot of sense to implement.
One last thing. After you configure client access to your router in “RoadWarrior” mode and connect the two routers in “Site to Site” mode, you will need to specify on your router in the route table which traffic (for which IP subnet addresses) to forward to the “Site to Site” VPN tunnel.