I own a Kickr Core and used to own a Kickr Snap, both great trainers, if it is in your budget I would recommend the Core as it is direct drive. The bike you use with the trainers does not really matter too much, just as long as it works. If you are going to use it just inside then I probably wouldn’t pay very much a 1000 euros should get you an extremely good bike for Zwift. If I had the choice I would spend less on the bike and buy the Core with the money you saved.
The Snap and the Core both have power meters built in so there is no need to use the Assioma (which I own as well incidentally!) with the trainers. But, you can if you want to.
The accuracy of the power for the Core is ± 2%, the assioma ± 1% and the snap is ±3 so TBH they are all fairly accurate if they are set up correctly and calibrated.