https://sagan4alpha.miraheze.org/wiki/SizeThis one specifically says not to use "microscopic" as a size measurement.
I believe "cell wall" has occasionally been used as structural support, and cell membranes do seem to be a means of structural support.
For comparison, the largest virus known at time of writing, Pithovirus sibericus, is 1,500 nanometers, or 0.0015 millimeters. That's bigger than the average size of members of the genus Ostrococcus, an exceptionally small class of algae with an average size of 0.8 micrometers (0.0008 mm). Since this eats other, smaller microbes, presumably ones significantly smaller than yourself, you'll need to make sure that, at least in its feeding stage, it's big enough that it still has something to eat.
"meant to disguise their identity and trick observers into registering them as something less dangerous." Meant by whom?
These have such a novel lifestyle that making a few references in the description to real-life microbes with similar lifestyles could boost its plausibility.