Generally, it's TOKENS (or coins, or TITO's) -- not chips -- that are inserted into slot machines.
Some people use tokens and chips interchangeably, but not in the chip collecting community.
(Strictly speaking, chips with a cash value on them are know as "checks", but that's another story...)

One exception is when "clay" chips were modified with a metal ring at Harrah's Reno & Tahoe locations to make a $5 chip-token that was used in then high-denomination slots. The experiment didn't work very well, but some of them survived to be collected. You can see 3 of them on the Chip Guide website. Here's one of them:

Regarding your RFID questions, you can learn about RFID's generally by searching the term on Wikipedia, or elsewhere.
Some RFID's are read-only and others are read-write, as you're aware from the nature of your questions.

My guess is that GPI offers both types of solutions, depending on what the customer wants and is willing to pay for.
Typically, chips at $5 or less won't have RFID's, for cost reasons, but that may change over time.

To get more publicly-available info, here's 2 sources for reading--
GPI's website pages on RFID's at:
http://www.gpigaming.com/rfid-technology

GPI's financial report (10-k filing). See page 4 in this document:
http://app.quotemedia.com/data/downloadFiling?webmasterId=101533&ref=10161993&type=HTML&symbol=GPIC&companyName=Gaming+Partners+International+Corporation&formType=10-K%2FA&dateFiled=2015-03-20