Haven't ridden in over a decade, at a loss of what kind of bike to get!

So my SO has decided to purchase a bike for me as my graduation gift, I only need to pick one out. I don't want to spend (or rather don't want him to spend) a lot so I'm thinking around $300 price range. I've never ridden a road bike, but the hunched over seating position doesn't look like it would agree with my back (willing to test one out though). I'm considering a hybrid for the most part, but have heard mixed reviews and a lot of advice saying to just buy a road bike or a MTB. I do not plan to go out on trails, mostly on roads, perhaps a few well packed dirt trails on rare occasion...but mostly streets. Comfort is a factor (of course!) but I'm willing to throw in for extras (like a more comfortable seat and pedals than just the stock). I'm not interested so much in speed, but nothing too pokey either (I'm not planning on racing, just biking to random destinations around town ect). My SO may end up getting back into biking, and he's always had a road bike...so I would like to bike with him, so being able to "keep up" may be a factor.

I'm hoping people more experienced than I can lend me a hand. My first bike was given to me and was some sort of clunker that served me well (all I can recall was it was a Mt Dew promotional bike and had thick tires, was heavy framed, more upright seated position, and heavy duty tires that NEVER went flat on me from punctures lol). So obviously I know nada about bikes! I've been dying to get back on a bike, I used to live on one as a kid...my Mom joked I slept with it in my bed