Questions about Ethernet Cabling

PLEASE READ: This is not a thread about the merits or demerits of audiophile-grade ethernet cables, or any cable for that matter. If you don’t believe in spending extra on expensive cables, I respect your opinion but please don’t turn this into a point of contention.

So before I ask my questions, let me describe how internet connectivity is setup in my house:

- [Home office/study] The modem (AT&T), router (Google Nest/Mesh), and switch ($25 TP-link basic switch) are located in the home office/study. I also have a second system in this room as well as other stuff connected through the switch. In other words, I can’t move the switch to another room.

- [Media room] The main audio system is located in the media room which is in the diagonally opposite side of the house (single story). This room has the ENO ethernet filter connected to the Innuous Zenith MK3 streamer, and so on.

[Long ethernet cable] A very long run of ethernet cable (CAT 6/over 100 foot) runs from the [Home office/study] router and terminates into the [Media room] ethernet jack/wall plate. This was done by the builder and it runs through the attic.

- [Media room] From the [Media room] ethernet wall plate, I then use another 6 foot ethernet cable (also CAT 6) that goes into an ENO filter and then on to the Innuos Zenith MK3 streamer.

So here are my questions:

1. Is it worth upgrading only the so-called last-mile ethernet cable, i.e. the one between the [Media room] ethernet wall plate and Eno filter while I continue using the long CAT 6 cable [Study >> Media room]? It is going to be difficult, if not impossible, to replace the long-run CAT 6 cable as it goes through the attic where several spots are not reachable without tearing down some sheetrock.

2. Is it worth adding a second audiophile-grade switch (e.g. uptone) in the media room while leaving the one in the study as is? Or is it better to upgrade the switch in the study first and place the cheaper switch in the media room? Or do I need to replace both switches (not prefered as it adds to the cost)?