SB 143 does not take effect until Jan. 2, 2020, unless back-room shenanigans take place or the unreliable Supreme Court finds some way to contort the law. Stocking up via private sales should take place as soon as possible; don't delay.
SB 143 essentially implements Question 1. The chief difference is that SB 143 requires private background checks use the state, rather than the FBI system. Dealers will still charge for their time to run the checks and do the paperwork, which will run $25-100.
The Brady exemption for CCW holders that applies to dealer sales/transfers now, will not apply to private background checks. This creates a two-tired system for background checks at the dealer.
Dealer retail sales (or receiving an online purchase shipped to the dealer)
A private person wishes to sell a firearm to another private person, they must first appear in person at a licensed dealer who will conduct the background check through the existing federal NICS protocol. Sales can still be arranged online and at gun shows. Between the request of the background check and the actual sale/transfer of the firearm, the licensed dealer takes possession of the firearm. If the background check is delayed or denied, the owner needs a background check to get the gun back from the dealer.
The exemptions to the law are:
Those are the only exemptions; there are no other exemptions whatsoever. Sales/trades between CCW holders are not exempt from this law and must proceed to the dealer as above. There is no provision to do background checks through law enforcement.
How Gun Sales Will Work After Jan. 2, 2020
How to Borrow a Gun after Jan. 2, 2020
How Not to Get Caught Making an Illegal Private Sale
The law is basically not enforceable unless you or the other guy makes a confession, runs his mouth, or the other party is a snitch/undercover cop.