That's correct. If you can do it with your setup one of the better systems is a continuous length of sanitation hose (or whatever else you're using) from the toilet discharge to the waste tank with nothing in between in the way of fittings, valves, or other gizmoes.
This system would be the more evil of the two main choices (and there are others) which are an RV-style gravity flush toilet or a marine-style macerator flush. The macerator is much more complex and requires some periodic maintenance and replacement. If someone puts something in the toilet bowl other than human waste or lightweight paper products you will get to perform maintenance on the system. On the other hand an RV-style gravity flush toilet will deal with anything small enough to drop through the rather large opening at the bottom of the bowl.
The electric macerator toilet is noisy, so depending on your layout if you have a light-sleeper partner (especially a grouchy-when-woken one) that could be annoying.
Also consider (depending entirely on your intended use for the bus and your personal opinions) that the macerator draws a fair amount of power while it's running so that might not be good if you're minimizing power use for an off-grid conversion. It also uses a fair amount of water to mix with the waste as it pumps it to the holding tank.
The marine-style toilet (even the manual pump models) have the distinct advantage of placement. They do not need to be over the holding tank to which they're sending their waste. They also do not require a hole in the bus floor for the waste dump.
I lean toward the RV-style toilets due to their simplicity and tolerance of use but they may not work in a specific floorplan; the marine-style toilet gives you much more flexibility albeit at the price of noise, maintenance, electrical load, and perhaps water use (this is entirely dependent on the operator, someone with a heavy foot (or hand) on an RV toilet can use a lot of water...maybe even more than the macerator toilet).
As always it comes down to what works best for you after you weigh all the options.