Well, welcome to the land of shitposting, fandoms and probably the most weird, satisfying and funny chains of engagement between a few users in here.
Posting is very comfy, since you can choose what'll be the focus of your post, be it a link, images (10 per post), text, video, etc.
There is the old version and the beta version of the Post Editor, both are good, but the beta one has other functions like, choosing text color and other things. You can attach links, images, pretty much like here, I recommend using hashtags obviously to appear in the result search when you type a specific word, as well, tagging works really good for when people want to make a section in their blog so other can see specific content tagged with it.
You can create different blogs with just one account, yes! You can have your main for whatever you like and then have blogs to either focus on something different, be it fandoms, keep your comic clean and organized (Especially if you don't want your posts to get losts between other content or reblogs)
Appearance of your blog can be totally modified, there are Themes created within the community or the ones recommended by the site, you can totally custom your blog to your liking, be it color, appearance and all. I personally prefer the default one since I'm very used to it, but there are other ones with interesting features such as Menu's, biography, galleries, etc.
Liking doesn't work like in Twitter or Instagram, it won't be seen by your followers nor will help you reach a wider audience, liking is basically a storage unit. The real way for engagement is through reblogs, and that can go very funny sometimes, be it someone answering with a gift, text or for some unknown reason but still feels very appealing, through hashtags.
Also, Tumblr has Neil Gaiman