Ali - you have plenty of choice, comes down to what you want to spend
Unless you go out with a Guide, I'd avoid the Loch for a day trip - too much local knowledge needed to find fish.
River Ness:
The Inverness AC water is well worth a punt, especially if the water is low-ish.
Of the two Ness beats on FishPal I'd plump for Dochfour for a day. They had a belting season last year, in part thanks to low water conditions.
River MoristonAvailability can be the snag, but some belting water (as long as the Hydro are generating) and super well-known for the 'spring' run:
https://www.glenmoriston.co.uk/fishing If it were me, with some spare cash then I would probably opt for this as my personal choice.
River OichLots of local knowledge needed, try Ala MacGruer of the Oich Fishings on: 07763 108 125
Grahams, the tackle shop in Inverness, may have other details for the Oich -
https://www.grahamsonline.co.uk/That's a start for you
H