Ingress Filtering Questions + uRPF

Yes, someone allowed me to read MUM archives, very dangerous!!

Two questions, lets do the easy one first.

Q1. /ip settings set rp-filter=strict Or /ip settings set rp-filter=loose

I have a BELL FIBER Connection on a VLAN (not ppoee) and an EASTLINK basic cable connection.
According to the mum for dual or more wan assymetric i should be using LOOSE. Is there any harm to keeping it strict?
Could strict interfere with Ip routes to the secondary ISP email or other weird shenanigans?

Q2. /ip firewall filter add action=drop chain=forward
comment=“spoofed from AS64501“
in-interface=$interface log-prefix=”“
src-address=!192.0.2.0/24
https://mum.mikrotik.com/presentations/BD18/presentation_5413_1526307143.pdf

WHOAH, that went zing… That rule blows my socks off and frankly I don’t get it. A breakdown would be sweet and then I can make a decision to implement it or not.
I do have firewall bogon block raw rule already in place plus blacklists etc and thus any way to become more efficient and effective is continually a driving factor.