The concentrates would be stronger than the flower you remember for sure, but the flower may or may not. People do tend to go for the highest THC they can right now though, so if that’s not what you want you might ask for lower THC or high CBD.
Rosin is basically just the result of heating flower a bit and applying a lot of pressure to squish the good stuff out. Some of the other concentrates are extracted with butane or other solvents...if they’re done by professionals they should be fine, but I like the idea of rosin better.
You can learn a lot hanging around here, but there are sites like leafly.com (and many others) with a lot of information aimed more at the general public if you don’t want to delve too deep into forums like this. If you’re very interested in vaporizers though, this is the place to be!