Pre-purchase Question: Migrating Boot Drive to SSD?

I'm looking to buy my in-laws a new computer. Their needs are quite modest, so they don't need a high-powered machine, which is why I'm posting this in the Inspiron forum. However, I would like to get them a fast SSD for improved performance. I have a couple of SSD-related questions:

1. Oftentimes, there are really good specials available on specific machines that only come with a simple HDD. I've migrated HDD boot drives to SSDs before, but usually they were just a single partition. Is it possible to migrate everything, including recovery partitions (or whatever Dell puts on the original drive) so that it's indistinguishable from the original drive? Does this impact the warranty?
2. I've used SATA and mSATA SSDs before, but not the newer form factors that allow for really fast SSD speeds (faster than SATA). How do you use these with an Inspiron or Vostro or XPS? Are they small cards that simply get plugged in (like mSATA) or are they large cards that get installed in the PCIe slots? What do I need to look for in the specs to ensure that I have the option of installing a superfast boot drive? Do I need to be concerned about power draw?

Bonus question: If my in-laws only use the computer for basic web-surfing (i.e., lots of chrome tabs open, but no gaming, etc.), what kinds of upgrades give the best bang-for-the-buck, both for now and to delay obsolescence later? E.g., is it better to move from an i3 processor to an i5? Or is that money better spend moving from 4GB RAM to 8GB or 16GB RAM? Will more cores really matter? I just don't have a good sense of which will impact performance the most for their use case.

Thanks for any help!