Mig 21 size question

The MiG-21 is indeed a small aircraft, as far as Mach 2 modern fighters go. And the F-84 being typical Republic, is on the large side.

F-84: Length-11.6m; Wingspan- 11.1m; Weight (empty)- 5200kg

MiG-21: Length-15.76m; wingspan- 7.154m; weight (empty)- 5842kg

So yes, they are similar sized aircraft.

With the pitot, the MiG is about 10feet longer than an F-86, which works out about 1.6inch in 72nd. So take the pitot off, and no, there won't be much difference.

But different brands can  produce kits of a slightly different size. I used a PE set designed for an Italeri MiG 23 on a Hase kit, and it was clear the Italeri kit is bigger than what I was building, at least from the cockpit.