Nah, don't worry about those things.
None of those ever stopped anyone from making good music.
And in a lot of ways you seem to overreact.
You don't have to downsample your 24 bit track, you can upsample the 16 bit track.
I mean, a lot of pop and electronic music is basicly made up of 16 or even 8 bit samples layered, often first going through analog and then back to digital conversion.
And guess what, noone is whyning about that.
In the end you will have to make it sound good, not the bit-depth.
As for effects, you don't need the material to be in 24 bits to enjoy better resolution plugins.
Altho 24 bits does give you more headroom which makes recording and mixing easier.
And of course all tools have at least a 32bit floating point internal bus so you always get the maximum quality out of any bitdepth material.
For compressor plugins samplerate can be important.
Since the plugin operates on the samples and the samples near nyquist rate don't acurately describe the waveform they become less precise for higher frequency trancients.
But then you're talking very high end and noone will expect that from a home studio.
And besides, if you use material from cd then the last thing you propably want is more compression.
Point is you propably have much much better tools and a much better possibility for a good sound then ever before.
Use it.