It is possible to just change the calipers with hydraulic disc brakes but it's best practice to replace both the level and caliper in one go.
Things to consider when using different brands of hydraulic brakes and calipers:
- The master cylinder volume and slave cylinder are matched to the lever stroke and braking caliper of each system. By changing part of the system it could affect brake performance.
- There could be differences in the sizes of the hoses between those brands.
- The braking systems could use different fluids. You don't want to mix a mineral oil brake system with a DOT fluid system or the internal parts will be damaged by the different type of fluids.
But all that said, if both systems look similar, use the same fluid type and fit together, then it should work OK.