I too have overkilled my system with ferrite much the same as Huge
I took a leaf out of the network install instructions from companies like Cisco & Ricoh, they recommend ferrite on network devises on both ethernet & power supply, in some cases more than one & also numbers of turns around the ferrite.
I use TDK throughout, make is not important but selecting the “right” mix can be confusing, TBH provided you use the commonly available types you find on Flea-Bay & Amazon, you won’t go far wrong.
Where cable size permits I’ve used large sized ferrite & passed the cable thru the core a number of times – NOT the ethernets tho’..
I have ferrite on both ends of all Ethernet cables
NDX-Switch, Switch-NAS & Switch-Hub (router/switch)
These are all Supra Cat7a & are screened - not sure what/how/if ferrite works with screened cables, but I cannot detect anything detrimental.
Power cable (screened) to the various SMPS power-strip,
Power cable to the Synology SMPS
All SMPS DC output cables & that includes adding additional ferrite to those that already have one factory installed.
Phone cable connections to Hub & Phone.
Phone lines are probably the worst RFI noise sources especially if your property is via overhead cable, less so if underground & less still if you are on optical – remember optical with BT Infinity is only be to the local distribution cabinet somewhere in the neighbourhood & it’s still a wire cable from the cabinet to your house. Adding ferrite to my Hub phone supply made a noticeable difference in that a www page without ferrite was hesitant building the page graphics over a number of stages, with the ferrite it’s invariably a faster & one stage page build.
Yes it might be overkill, but I have yet to hear or see anything detrimental.