I believe that amount of data won’t be an issue using the standard bubble search functions, as long as you filter what you’re retrieving well. It’s worth reading through this thread if you’re concerned about scaling: Performance Q&A guide
You almost certainly won’t be able to use the Search & Autocorrect plugin to search through that amount of data. The plugin (like all bubble plugins at the moment) works entirely in the front-end, which means that to search through 20,000 items, the browser will need to retrieve 20,000 items first. I’ve never tested it with that number but would assume it would take forever and maybe crash the browser. If you can filter it first to a more manageable number then you can use the plugin.