Travelling from NL to Poland by touring bus sucks so bad IMO; it’s cramped, it shakes and vibrates so much, it often doesn’t smell great, there’s one tiny toilet for everyone and it isn’t clean by the end anymore, and if there’s an airco it probably won’t work. If I’d known, I’d just visit Poland a season later and save money for an airplane ticket, instead.
The one I’ve been in you could bring food and consume it in the bus, they also made a few stops at tankstations where you could buy snacks and drinks just so you could consume them in the bus.
IMO, trains and planes are better; they travel calmer, are more comfortable, and cleaner, too. At least from my sample size of 1 bus, 2 international trains and a dozen or so airplane rides (mostly to other continents).
Planes are more stressful checking in and out, but you can bring much more baggage and it’s usually cheap to do so. Trains have a fraction of the environmental impact. That’s what I base my decision on, busses are out of question for me.
EDIT I forgot the bus took far longer than it had to, I don’t recall the exact delay but a train would’ve never done that, and with a plane the delay would be me spending time on a nice® airport