The simple answer is no you cannot pick and choose which parts of Open
Office or Libre Office you want.

The long answer is that the difference in size between a full install
and partial one is minimal anyway so there's no advantage to be gained
from *not* having the full suite. All office sites have a large core
that is required no matter which sections of it you actually use, it's
not like selecting just 1 part out of 4 results in an installation
that's a quarter of the size - it just doesn't work that way

Ever done the 'custom install' in MS Office and checked the 'estimated
space needed' as you select/de-select options ? You'll have seen that
this doesn't change as much as you might have though.

If you are so short of space that a few tens of Mb are important to
save then you have far greater issues than which parts of an office
suite you are needing !! So just ignore the bits you don't use.

BTW - if you really delve deep into the guts of any OS you'll find a
whole mess of stuff that you probably will never use but trying to
prune out those bits is a mammoth task, and doomed to trash the OS :-(

Re: Word Perfect. If you are wanting to still use this then you might
investigate 'Play on Linux' which although is aimed at games it also
can help installing other programs under Wine too. The alterative is
running Windows in Virtual Box just to use that one program - not as
onerous as it might seem and I do this as well for the few programs I
have to use that have no Ubuntu equivalent.

PS - Libre Office opens WP files but cannot save in them. Struggling
to see why you are so set against using the Open Document formats, is
there a good argument against this or is it just the familiarity of WP
that's preventing it ?