I recommend having it done by a professional graphic designer. The best tools won’t automatically produce high-end graphics easily. Check this: https://www.easyresearcher.com/
I recommend downloading the pdb file of the biomolecule (or a similar molecule), visualizing that using available free softwares.
For more complicated illustrations:
Simplest way to get a professional scientific drawing or a graphical abstract with low cost for your research report or paper:
https://unitechlink.com/scientific-illustrations/
A team of scientists and artists works on your illustration/journal cover/schematics instead of only one illustrator. It's quick and the price is very reasonable (with first-time-order discount).