This hotel was a very nice surprise overall. The gym is massive (it is run by a separate company (https://www.parkplazacardiff.com/laguna-spa-and-gym/) and it really has everything you need even for the long-term staying. Hotel also has a swimming pool which is maybe 20meters long, so you can have a decent swim in it as well.
I wasn’t able to find a picture of the freeweights-barbell-dumbbells area, but they do have a lot of those also. The website only have photos of the cardio and machines area (which sucks).