I don't know why Fabius Maximus thinks that tidal forces would be too strong in a double planet or a a habitable moon of a gas giant planet.
Part One of two: Two habitable planets orbiting the same star.
But If Fabius Maximus thinks that is the case, the next logical step would be to have two habitable planets orbiting the same star in different orbits, close enough together to both be in the habitable zone of their star and have similar climates.
In old fashioned science fiction stories from the first part of the 20th century, it was quite common to depict Venus, Earth, and Mars as all being habitable planets within the Sun's habitable zone.
Modern astronomers still tend to believe that it is possible for more than one planet to orbit in the habitable zone of a star and thus have temperatures suitable for life.
Of course, from time to time a different team of scientists will team up to calculate the inner edge, or the other edge, or both, of the Sun's habitable zone. Thus there are several different estimates of the size of the Sun's habitable zone.
In this list here:
There are some widely varying calculations about the size of the Sun's habitable zone.
Hart et al in 1979 made the narrowest estimate of the Sun's habitable zone, between 0.95 AU and 1.01 AU. That estimate would make it very improbable that any star could have two planets in its habitable zone.
Kasting et al in 1993 made the most commonly used estimate of the Sun's habitable zone, with a conservative zone between 0.95 and 1.37 AU, and an optimistic zone between between 0.84 and 1.67 AU. It would be much more probable to have two planets orbiting in Kasting's conservative zone than in Hart's, and more probable still for Kasting's optimistic habitable zone.
Other estimates put the inner edge of the habitable zone as far in as 0.38 AU (Zsom et al, 2013) and the outer edge as far out as 10 AU (Pierrehumbert and Gaidos, 2011).
Astronomers have discovered hundreds of systems with more than one planet, and those systems vary widely in their orbital and other characteristics.
The orbits of Kepler-70b & c are separated by only about 0.0016 AU or 240,000 kilometers, and it is possible that there could be a third planet orbiting between them.
The orbits of Kepler-36b & c are separated by a larger absolute distance but a smaller relative distance, with the orbit of Kepler-36c only 11 percent wider than Kepler-36b.
The star TRAPPIST-1 has four potentially habitable planets in its habitable zone, and they orbit very close to each other.
The orbits of the TRAPPIST-1 planetary system are very flat and compact. All seven of TRAPPIST-1's planets orbit much closer than Mercury orbits the Sun. Except for b, they orbit farther than the Galilean satellites do around Jupiter, but closer than most of the other moons of Jupiter. The distance between the orbits of b and c is only 1.6 times the distance between the Earth and the Moon. The planets should appear prominently in each other's skies, in some cases appearing several times larger than the Moon appears from Earth. A year on the closest planet passes in only 1.5 Earth days, while the seventh planet's year passes in only 18.8 days.
The orbit of TRAPPIST-1e is only 1,050,000 kilometers wider than the orbit of TRAPPIST-1d.
The orbit of TRAPPIST-1f is only 1,380,000 kilometers wider than the orbit of TRAPPIST-1e.
The orbit of TRAPPIST-1g is only 1,250,000 kilometers wider than the orbit of TRAPPIST-1f.
The average distance of Earth from the Sun is defined as 1 Astronomical Unit, or AU.
If you make the star in your solar system exactly as luminous as the Sun, you could put one of your habitable planets at a distance of 0.96 AU and the other one at a distance of 1.0656 or 1.070 AU. The inner planet would receive slightly more heat from its star, and the other planet would receive slightly less heat from its star, than Earth gets from the Sun. The orbits of the two planets would be separated by about 16,170,000 kilometers.
Part Two of Two: Two habitable planets orbiting two different stars in the system.
In a binary or double star system, there are two possible types of orbits for planets. One is a circumbinary or P-type orbit, where a planet orbits around both of the stars. The other is an S-type orbit where a planet orbits around one of the two stars.
Since the luminosities, masses, and orbits of the two stars in a binary can vary widely, there are many binary systems where a planet could not have a stable orbit in the habitable zone of either star or around both of them. But there are many other binary systems where planets can have stable orbits, either P-type or S-type, in a habitable zone.
The OP asked for a binary system with two habitable planets in S-type orbits, one around each star. That is certainly possible. It has been calculated, for example, that planets could have stable orbits in S-type orbits with the habitable zones around both Alpha Centauri A and Alpha Centauri B.
According to one list, the closest known distance between stars with a planet orbiting one of those stars is about 12 to 17 AU, with a planet orbiting about 0.7 AU.
In my opinion, it would probably be safe to have the two stars in the system have a nearest approach of about 10 to 20 AU, and each have a habitable planet orbiting it at about 1 AU, as well as other planets in S-type orbits around either star, and possibly other, not habitable, planets in P-type orbits at great distances from the two stars.
And of course there are various scientific discussions about which separation of stars is best for long term stable planetary orbits.