To quarantine or not is a personal choice you have to make based on your own evaluation of the risks.
Would you be very upset if you got pond snails from the plant? do you have expensive fish that you’d be devastated to see get sick or you don’t want to medicate your main tank? Best to quarantine. Do you not have much in your main tank; thoroughly trust your lfs or wouldn’t mind medicating the whole tank if something comes up? then skip it.
I almost always quarantine everything but I’m only looking for the most common of issues so I may only do a week or so. It’s insufficient time for me to be absolutely sure the fish are free of everything but it’s a level of risk I’m usually willing to accept. For plants I usually rinse well in tap water then put them in a bucket for a few day’s just to look for snails on the side of the bucket. Again; insufficient to completely ensure no hitchhikers but it’s the level of risk I’ve found I’m okay with.
The proper quarantine technique if you really REALLY want to protect your main tank is the new fish spend months on their own then an inhabitant from the main tank moves into the quarantine tank to check for diseases the new fish may be asymptomatic for. As you can imagine very few people are doing quarantine with that level of rigor, instead people determine what level of risk they are willing to accept.