The nature of “Free Software” means you have to try different vendors and hope they all work together.
I have nothing against free software, in fact we use OpenOffice and LibreOffice in our own business and my personal devices. I prefer them to any Microsoft product as they use a lot less resources, less likely to crash, and even if they do fail they almost never fail to recover the file.
Either OpenOffice or LibreOffice are free for personal use. Even for business use payment of a licence fee is a voluntary option. We do contribute to them because we do want them to thrive and continue to provide alternatives to Microsoft and Apple products. This is even more critical now that Microsoft has decided to join the party for “Hosted Solutions” with their Office 365, so that they can extract money from users on annual basis rather than just a one-off payment.
OpenOffice and LibreOffice offer you full package including their versions of Word, Excel, PowerPoint, and Database like MS Access but this one actually works! The reason they use less resources is because unlike Microsoft Office & Apple where each programme is a distinct application, OpenOffice and LibreOffice are a single application.
This means if you have an Excel, Word, and PowerPoint open at the same time, you still only have 1 instance of the application running rather than 3 with others. This means you need less RAM and less CPU processing juice to run these programmes.
And yes you can open all variants of Microsoft files, and save your files either as native version (much less memory hungry) or as Microsoft versions so you can send them to other people who can open them too (xls, docs, ppt, etc.).
Now with the tricky subject of Speech to Text.
Unlike MS Office, these packages do not have a native application for this function. The reason is simple as this is a very niche requirement, and the effort in development and maintenance is too great for FREE software.
There are packages or add-ons called “Dragon” and “SpeechOO” for LibreOffice and OpenOffice respectively, but I can't comment on how good they are as I have never used them. If you are an Android user you can use your smartphone to convert speech to email, and then copy and paste the email to your word-processing applications such as OpenOffice or LibreOffice or even MS Office if you really must use it!
Here are links to help you:
OpenOffice - http://www.openoffice.org/
OpenOffice SpeechOO - https://extensions.openoffice.org/en/tags/voice-recognition
LibreOffice - https://www.libreoffice.org/
Dragon - https://www.nuance.com/dragon.html (Please note Dragon supports only the 32-bit version of LibreOffice & some functions are not supported.)
I hope this helps and do let me know how you get on as I will be very interested to get an update on this.