It could well be very relevant probably depending how close a noisy source is located to the incoming line.
Power lines absolutely cripple my line causing thousands of errors a minute.
I run the older version of these Tacima SC947 (older version has no test button), they can be picked up around £35
https://www.whathifi.com/tacima/cs947/review
I own I think 4 of the older version, I'm quite into HiFi and they definitely improve the sound (bring the base, and mids out). I'm also pretty certain they improved quality on my triple monitors on my PC (i'm a software dev run 3 monitors).
I also installed one at a friends house who was getting clicks into his Hi-Fi from his fridge, straight away improvement in sound quality, plus all the clicks into amplifier have gone.
Actually did a test with a power-line adapter on one, by connecting a power-line adapter into a mains conditioner, it did not fully filter out the power-line adapter, however it dramatically reduced it's speed, I can't remember what but was watching number in the TP Link power line ultility.
But you should definitely get one for your modem, they are not snake oil they definitely improve the mains. The other thing you should try is a twisted pair RJ11 cable, but only get the shortest run you need.
Another thing you can do! And there is some evidence to back this up, is double filter your VDSL line. Basically what you do is connect another ADSL/VDSL filter into the BT face place filter (so 2 filters in series), I do it and my connection is super stable.