Looking for a step down converter for my power supply

Hello dear Ti community.
I'm looking for some good step down converter for my power modules which are MeanWell IRM-30-24 // MPM-30-24.

I've got a few question regading this module and potential step down IC.

1) should I use CLC filter at the output of this MeanWell module before I feed step down IC?
2) should I use some kind of filter at the step down IC output (to minimize ripple and noise)?
3) does it make any difference if IC will work at higher freq for eg. 100KHz (PSU module is working at 65KHz).

I'm looking for some rather effective and yet simple solution to avoid linear/LDO regulators due to heat.
Because these in no 18VDC option for this module I'm looking for something that will be able to provide 20VDC that wille be further used for voltage regulators.

I think using LDO/Linear regulator to drop down voltage to desired level will be potentially cheaper but not that effective at all.

Both modules will be used as a bipolar power supply for powering analog IC's like opamps etc.

Thank you for any information and help ;)

Have a nice day.