Nick O'Dell has it right. To expand a bit on the last question:
What implications do blocking port 8333 have on my bitcoin daemon from getting transactions? Does it get less transactions or get transactions slower?
It has no impact. There are only ever 8 outgoing connections even if you disable this port or set listen=0.
If you set maxconnections= significantly lower than 8, then you could (I suppose) start to have problems. If your addnode= or connect= were connecting you to a few slow/intermittent peers.
EDIT:
"I believe, effectively, blocking port 8333 will only stop peers from connecting to me (stops inbound) and not me connecting to peers (does not stop outbound). Is this right?"
It just occurred to me that yes if you block the port on the device hosting the node, it will be blocked. But with IPv6 now becoming more available from ISPs you can get inbound connections on 8333 even if you did not use UPNP, nor port forward on your router (many domestic routers do not support IPv6 filtering).
