VA, USA to Ottawa, Canada
 

I am looking to visit some friends in Ottawa, and based on flights being so long/expensive and not wanting to have to rent a vehicle, I'm thinking of driving there. I would be driving by myself and only staying 2-3 days. Any thoughts on making the 10 hour drive, staying a couple days, then a 10 hour drive back? Also, insights in border control and customs would be super helpful, and I have a cat I would like to bring if possible.

Do you like driving? Are you a good driver? What age range are you?

Driving 10 hours alone in a car can be a challenge for some people. I'm a senior citizen and I enjoy driving so 10 hours in a car alone doesn't bother me. but I do find that I need a couple extra rest stops than I did in my younger days.

I can't help you with border crossing because it's been over 10 years since I've driven from the US to Canada so any info I would have is dated. You will have to check on what, if any, Covid Travel restrictions are in place during your period of travel. I can tell you that back in the day, the border crossings were a non-event - just had to show my passport, answer a few quick questions and I was on my way. The only real hint I can give you is plan your route and timing so you don't arrive at the border anywhere near "rush hour" other wise you'll be in for a long wait.

As for the actual road trip, I always found it helpful to make a brief rest stop every couple of hours. It gave me a chance to stretch my legs, use the rest room if necessary and kept me alert. I also planned on a somewhat longer stop for lunch. The most important thing was to immediately make a rest stop the moment I felt drowsy.

If you really want to take your cat across the border, you must check with your vet to get a health certificate to show at the border. I think that it is more trouble than it is worth.
There are two Amtrak trains that go into Canada. One goes to Toronto and the other goes to Montreal. Ottawa is served by ViaRail from both Toronto and Montreal.
Check on the status of your passport before doing too much planning.