Most American tourists find European trains a lot easier to use than they are anticipating; it's just that few of us grow up using trains.
I will warn you a bit about the situation in Brussels. As of this summer there was street-level construction to the northeast of Brussels Central Station. Temporary fencing (often totally blocking sightlines) took up sidewalk space in some areas, and it was hard to get oriented--at least for me. It was a challenge because of the location of my hotel (the Motel One on Rue Royale), but you may very well not see it at all. The walking route toward the Grand Place is in the opposite direction.
I'd recommend plotting walking routes on the CityMapper app just to be sure you don't run into a problem. I'm stubborn (I like to wander) and didn't do that; as a result, I ended up on a rather circuitous route on one occasion. Brussels has some hilly spots, so an additional thing CityMapper or Google Maps will help with is signaling challenging terrain via longer-than-expected walking times. The usual allowance is about 20 minutes per mile. They might estimate a bit more time if there are lots of intersections to cross, but if you see a significant difference (more like 15 minutes per mile), there might be a significant hill to climb. It's nice to know those things in advance.
Some bus stops in the area of Brussels Central had been relocated temporarily as of a few months ago. There was signage at the old stops, warning that buses were being rerouted, but I didn't find it easy to figure out the exact location of the new stop. I managed, but it took some extra time. CityMapper and Google don't always keep up with temporary bus-stop relocations. I didn't take any taxis in Brussels (I am beyond cheap), but that doing that at Brussels Central wouldn't be a crazy option under the circumstances.
I had a lot of trouble finding an escalator or elevator at Brussels Central that would get me up to street level. Expect that to take some extra time if you can't find someone to ask (and maybe even then). I never did find step-free access from street level down into the station. It's possible I just wasn't trying to enter through the best door. Perhaps there's a station floor plan on the internet that would have done the trick. I mention this situation because it's unusual to have such a struggle getting into major-city European train stations.
Brussels has three major train stations. Many trains stop at all three (in addition to more minor stations). Your hotel is likely to be closest to Brussels Central/Centraal. The other two stations are Brussels North/Noord/Nord and Brussels Midi/Zuid/South. One part of the area around Brussels Midi/Zuid/South is said to be not the greatest, so it has been recommended here that tourists not wander around randomly in that area. (Ask here for specifics if you need to go over that way.) I didn't spend any time near North or South Station, so I have no personal experience in those neighborhoods.
Domestic trains within the Netherlands are tap-to-pay. You must tap both in and out. There's one thing to be aware of, though: There are multiple train companies in the Netherlands, each with their own turnstiles in stations they serve. I think you'll always be on NS trains, but there may be turnstiles for other rail companies in the stations you use. It's important to pay attention to the logo on the turnstile to be sure you're using the right one. If you do not, you are likely to end up paying for the trip again when the conductor for the correct company comes along, and you could be fined. (I made this mistake at least twice during my month in the Netherlands but was lucky never to be fined; the conductors took pity on me, I assume.) You can see the NS logo here: https://nl.wikipedia.org/wiki/Nederlandse_Spoorwegen
