Nice! The Polaris ebikes (2014 and 2015) seemed well built, definitely from the ground up with custom drive systems etc. Glad to hear you like yours and congrats on the good deal you found. I don't have any tips to share about
the Vector specifically but the fact that it has braze ons at the rear seat stays should make a rack
like this one work alright (and it's super cheap). Depending on how much you need to carry and whether you'll be using panniers,
this rack is a bit sturdier and has more bars to separate bags from spokes/wheels. Definitely check out the rear dropouts and see where you'll be attaching a rack to make sure the mounting design will work and not collide with the rear disc brake rotor. You can always get
a beam rack like this but they do swivel a bit more and just don't feel as sturdy to me. Here's a short video I made a while back talking about beam racks, fenders and panniers for a full suspension ebike:
And here's a video about some fenders I tried, they didn't work all that well on rough terrain. Eventually the front one caught on the wheel and the plastic sort of broke.
As for fenders, it looks like the Vector has 26" wheels so you could get
something simple like this which are a bit wider for keeping splash down on your lager tires. I like that they are also full length and fairly affordable
