If you do a barebottom tank, acrylic is easier to keep. But if you use sand which I assume you will (coral sand, not the play stuff), it will scratch at some point. It's just unavoidable. You'll be careful, and for a bit you won't scratch it, but eventually you will. Sand, rocks, tools, etc. Something will scratch it, and it will piss you off! It is clearer than standard glass, but I don't find the tradeoffs worth it for smaller tanks. You can get Starfire glass, which is clearer than standard glass, but it's also softer and scratches easier.
Water changes, it depends. I shoot for around 30% every two weeks. I don't have a macro algae refugium on my current tank, so I do larger water changes than some. Some people do smaller changes weekly. Some do larger changes monthly. But if you can get 20-40% of the water changed per month, you're doing pretty good.
For power outages I have two backups. First, my Ecotech Vortech pumps have a battery backup on them. That kicks in anytime they lose power. It only powers them at like 25% speed, but any circulation is better than no circulation. Second, I have a power inverter that I hook up to my car to power the pumps at full speed if the power outage is going to last awhile, or if I need to power a heater or a fan or something if it's cold or hot
In the rare even it lasts longer, I borrow my dad's generator. We had a 2 day outage after a tornado a few years ago, and that got me through it