First off, welcome to Tropical Fish Keeping forum.
To your question. You will need a very much larger tank than even a 90g for several of the named fish. The Black Ghost Knifefish will (or should if healthy) grow to 20+ inches, and it needs a tank that is wider (front to back) than this so it can turn, at at least 3 times the fish's length. Our profile explains this more. Click the shaded name for the profile. A 90g will work for a time, but I am one who does not condone buying any fish that is potentially larger than the tank I now own; plans to upgrade later do not always come to fruition, and then the poor fish is the loser when it is stunted and unhealthy.
Clown loach also needs a 6-foot tank, and must be in a group. Profile explains more.
Dojo loach has specific needs like cooler temperature than may not be suitable for other fish, so this needs to be kept in mind when selecting the tankmates. It needs a small group of 3, being social, and it may well eat smaller fish [it grows 9-10 inches, but can reach 12 inches]. More info in the profile here too.
The Ropefish [this species is not in our profiles] can attain close to 2 feet, and should also be in a group, so this is needing a much larger tank too.
Profiles are under the second tab from the left in the blue bar across the top of the page. Info includes minimum tank sizes, minimum numbers, compatibility issues, water parameters, etc.
Aside from the above, if you have the space for the 90g i would recommend it over the 60g. We all buy a tank that we think will be sufficient, but within no time we find we need more tanks or larger tanks... so start with the 90g. It is a nice sized tank in my view; it has a lot of possibilities.