Swiss Day Pass

Karen, Your interpretation is correct. The Day Pass has the same coverage as the Swiss Pass and the GA (annual pass for residents).
Domodossola - Brig - Fiesch - Fiescheralp OK. Fiescheralp to Eggishörn not covered.
At Fiesch there is a 10 minute walk, or a bus, form Fiesch station to the cable car (not a tram).

I looked it up on the SBB website. The standard fare from Domodossola to Fiescheralp is CHF 45.80.
The Day Pass is "from CHF 52", and depending on which date, and how far in advance you buy it, it can cost more. I do not think that would be the cheapier option.
Were you looking at the "from as little as CHF 29 with a Half Fare travelcard"? If you have a Half Fare card, the normal fare is CHF 22.90, so it still isn't worth it.

Thanks for confirming. We'll probably do the day pass since we are not tied to specific trains and can be flexible, even if a few dollars more. We stayed in Fiescheralp in February for a couple days of skiing, and are looking forward to staying in this area in the summer with friends visiting from the US.

We'll probably do the day pass since we are not tied to specific trains and can be flexible,

Karen, standard Swiss tickets, the prices I quoted, are valid on any train on the date shown on the ticket.
If you are coming from somewhere else in Italy (Verbania), the Italian ticket to Domodossola may be train specific, depending on which train you take. After Domodossola Swiss rules apply and you can use any train (or stay seated on the same train).

The trains from Verbania to Domo are regional. Other reason I was thinking the day pass, are if we do some hiking after arrival and want to take other trams or train back to Fiescheralp. Still in the planning stages, but now have the info I need to make decisions. Thanks.

The Saver Day Pass can be a great deal, but in that case I'm not sure, as I think you can get a cheap SBB supersaver or Italian ticket to Brig if you can commit to a time, and from there it's very close (hence, quite affordable) to Fiesch.