Normal mainstream forums always tell people like you to forget a pass and book advance-just as you likely do with hotels-on the sites of the railways. It does not matter how long you stay in each town-but the total length of trip may do (keep it in 1 month)

ESpana-certainly in hi season/summer is very hard to get seats-and this can in practice only be done in person at counter. The direct hi-speed trains ES-FR are also expensive as supplmt and hard to get-though one can avoid these by using slower local trains.

You may also have noted there is a sea between Ireland and GB-that means boats/ships out of pass-but maybe with discount. Generally there are fairly cheap advance fixed booked tickets for boat+train.

So the question back is now: do you want to adapt/can be flexible and dont mind using these slower trains OR it is so fixed that this is out of the question? PLus what time of year.

I count 4 or maybe 5 days of travel where a pass might make it worthwhile-or not-or maybe. But at least you managed to fly over the routes that are even more cumbersome: PT to ES and train under Channel.

That really depends on how much you will be travelling on each location.

In a country like Switzerland I guess that you plan to travel around. Then it depends if you are travelling on routes where you travel for free, and use a travel day, or if you plan to go to the Jungfrau-region, where the Eurail pass only gives you a discount and no travel day is used.

Thank you!! We dont have enough time to take slower trains and we're travelling mid Feb to mid Mar 2023, so well and truly out of the peak time

At each destination, there's not much travelling within them, just catching Metro Trains, Trams, Buses & only staying in main cities or centered to see the main sites.

There is however Portugal to Porto & Sintra. 

Staying in Interlaken, then doing day trips to Brienz, Thun, Spiez, Jungfraujoch, just around Interlaken - are they part of the Eurail? Whether there's a little extra fee/discount?

Trains to Brienz, Thun and Spiez can be used with a Eurail pass. See this map with the validity of Eurail/Interrail in Switzerland.

On the trains to Jungfraujoch, you have a 25% discount and you don't need a travel day. It is expensive though. A full fare return is CHF 235 (for you then CHF 176).

Oh, thank you, that's good to know. 

Wow, geebuz!!!! Here we were watching youtube and they failed to mention the price . That's ok, it's once in a lifetime thing and we're coming from far, the Land Down Undah... I already gave the Glacier Express a miss coz I couldnt justify sitting and staring out the window for 8hrs and for double the Jungfraujoch price, and that's 1 whole day gone for us.

The Glacier Express is included in the Eurail pass. If you choose to travel in the normal coaches you don't have to pay any reservation either.

As being half Swiss I personally think that the Jungfrau-region is overestimated. It is very pricy and crowded with tourists. 

There are many nice scenic routes in Switzerland that are included in the Eurail pass. If you want to travel in the panorama coaches you need a reservation. Otherwise you just board the train.

https://www.swissactivities.com/en-ch/panoramic-trains-in-switzerland/

The Glacier express doesn't have normal reservation-free coaches. But the many regional trains on the same route do of course.

I fully agree. If you want to have stunning views, just travel e.g. from Brig to Chur via Andermatt, then to Sankt Moritz and/or to Tirano. No reservations needed, all included in the pass.

Oh I see, thank you. Will look into it further. 

Thank you for your input, I appreciate it. I'll keep re-searching and asking questions. :)

Just looking at those stops; Brig to Andermatt and Chur, I think I'd prefer this, as we'd be able to hop off and on and visit these towns, rather than just passing by. Thank you!