Route planning on laptop - Epix 2

take a look at plotaroute.com for me it is the best platform

if I don't use the connect app/explore then I tend to use Komoot.

While you can't sync to basecamp you can export a track, which you can then upload to your watch.

Hi, I use OpenMTBMaps for many years now - just brilliant. Basecamp is still my repository to manage tracks. I export tracks from Basecamp and upload the tracks to Garmin Connect using the web version. Please mind, in Garmin Connect a track becomes a course. From Garmin Connect Mobile I send the courses to my Garmin devices. Actually I'm using GPSMAP for MTB navigation as I find it more convenient. My watch is just the backup for navigation but it also works very well.

I would use Basecamp to manage routes, but I cannot use Topo maps since I have them on my Epix but it doesn’t sync to Basecamp, I don’t see any detailed maps on the software. 

You can install maps from OpenMTBMaps on your laptop and use them with Basecamp. You don't need to sync with your Epix. There are tutorials, instructions and a lot of documentation available on the website of OpenMTBMaps. The installation process of a map is straight forward and not difficult.

Thanks and sorry for the late reply.