There is a minimum "safe" distance between planets which depends on tidal gradients and gravitational disruption of orbits.

You will recall the common "wisdom" that the asteroid belt is a failed planet due to the proximity and large Mass of Jupiter. This may be true, or may be a fiction.

Certainly, in simulations of planet formation, embryos that are too close get swallowed, ejected, fragmented, or moved.

Nobody is really sure about the right numbers to plug in but for my course on planetary formation I use a simulator which includes a gravitational "stand-off" term based on minimum observed proximities of satellites of the gas giants, and of the planets:

M/(R2-R1)^2<60

The Mass of a nearby planet M divided by the separation of orbital radii (R2-R1)^2 must be less than 60.

All units measured in AU and Me

So, for your proposal, for two closely orbiting terrestrial planets at minimum separation:

M=1
R1=1

1/(R-1)^2=60
hence
(R-1)=1/60^0.5

R=1.129

So IF this equation were correct, then your model is plausible, at the upper end of radius that you quote.

Notes:

1) This presupposes a "quiet" system, so don't go putting gas giants too close or that will mess everything up

2) A planet round our Sun at 1.129 Au would have a "bare rock" mean surface temperature of 245 K (some 15 K colder than Terra). With an identical atmospheric greenhouse, it would have a mean surface temperature of 270 K, although this would lead to a lot of ice, high albedo, and less global warming so a bit of a runaway iceworld.

You might get away with things if if you had a better greenhouse, a thicker atmosphere in general, or a favourable orientation of plates equivalent to some of earth's warmer Epochs,

Alternatively, move both planets closer to the Sun (or dial up the Sun by making it bigger and hotter) and have one doppelganger warmer than Earth and the other colder, but only by a few degrees each way

3) You can make the temperatures more equal by having a MUCH hotter sun and MUCH larger orbits, but still the same orbital separation. However, stellar lifetime degrades rapidly with Mass and anything more than about 3 Ms has a lifetime less than 1 Ga.

Still, given the scaling of Luminosity and Mass, such a Sun would be ~20 times hotter than Sol and orbits for the G-spot (Goldilocks, not the other one) would be ~4.5 AU and the two planets would differ by only a couple of K in equilibrium temperature...

4) If you want, I can sell you my Star and Planet calculator that works all these things out. :-)