I have been using LibreOffice for over a decade now to do schematics and diagrams for illustrations in publications and patents, probably since it was OpenOffice 3.x or so (been so long that I forget). It will probably read your old Visio files, and I would search your old Visio version for the templates (since you paid for them already)
LibreOffice has continually gotten faster and more stable, and is in many ways (not all) better that MSOffice (that I also use extensively). Since my new work computer came with Win 10 and Office 365, I have seriously considered moving all new work to LibreOffice. There will be some pain points, but the forced updates, pop-ups, and adware (from MS and affiliates) just really suck.
There is one gotcha in LibreOffice Draw. It only does dimensions to two decimal places (WTF?). For me, this is not really a problem since I use it for diagrams and illustrations for work. But, if you want to use it as a poor man's easy 2-D CAD, this limitation will get you sooner or later...
I will be attempting to use LibreOffice Writer for my next technical article. Why not LaTeX, you might ask? Because I have to remain compatible with MSWord and articles are passed back and forth. Writer has excellent Word import/export capability. So excellent, in fact, that I routinely use it to fix broken Word documents by importing them into Writer and exporting them back into Word, at which point they become usable in Word again...
An aside on LaTeX. I wish I could use it for work. It took me a long time to learn, but at least it puts figures in the right place and has consistent, fully functional, and flexible cross-referencing and numbering. I never use this functionality in Word anymore. It is broken beyond belief. I hope Writer is better in this respect.
Thanks for listening, doc...
Cheers,
John