My question is, once in the US what would the situation be regarding changing jobs and visa security? Is it easier to get a new job once in the US when I decide to, or is it the same struggle as getting an H1B visa?
If your company qualifies, and your job role qualifies, a L1(A or B) is the most likely route.
Do you work for a large multinational? L1B is for folks with specialized technical knowledge. The good news is, L1 visas are dual intent (like H1B) so you can later file for a green card. The not so great news is L1B has to go through the Permanent Labor Certification program.
I would plan on working for the company that you get the L1 visa with for at least a few years. Eventually you will be able to get the greencard, at which point you are free and can go work for anyone you please. 5 years after getting the greencard you can file for naturalization and become a passport holding citizen.
Lots of info online. Google for something like “L1 visa greencard”