My first contact with RS, then Radiospares, was in the early 70's.
The notable thing is what a small range they carried, small enough to be published in an A5 thin catalogue that ballooned into a 6-inch A4 pack of catalogues in the 90's.
What I mean by unbranded was the fact that you could buy say, a Bourns potentiometer, but it wouldn't be printed with Bourns, but had "RS" on it. Nothing in those early catalogues carried brand names.
As an aside, I bought some cheap boost convertors that had a blue pot on the board. The pot had some name on it that closely imitated Bourns, even to the point of the capital B of Bourns had the trademarked tail on the B.
At least by using any of the big distributors, you should get genuine items.
Apart from the free delivery that pulled in a lot of business from private buyers, RS had expanded into things like DesignSpark and their own PCB design software to attract enthusiasts.
I haven't used it, but it wouldn't surprise me if it produced a BOM with RS part numbers.
I think this delivery price hike, £4.95 + VAT on orders less than £30 has been slipped in under the cover of coronavirus and losing a lot of budding developers and electronic hobbyists might hurt them in the long term. Farnell now looks good value at £3.95 plus VAT, free for orders over £20. An order I was going to place with RS yesterday was rapidly cancelled and went to Farnell instead, so Farnell win, RS lose.
As you say, Farnell has their Multicomp and ProPower cheap ranges and RS's RS Pro range the same.
I also rate Digikey for their huge range and occasionally, I use Rapid/Conrad, but "Rapid" doesn't apply when it comes to next day deliveries - non existent