If you sub, you get access to everything, plus even if you cancel after just one month you retain the status of “Premium” account, which means things like gold limits, trait limits, mount access and other limitations of F2P are lifted for life on any characters that you played or created while a VIP.
To further answer your question on non-expansion regional quest packs: Given the packages you purchased, you’ve only got a handful of region quest packs that you need which you don’t already own. You get full access to all the starting regions for free with F2P, and from there you really only need the following regional quest packs to advance your characters to Moria and beyond:
North Downs - 595 TP
Trollshaws - 595 TP
Evendim - no cost to you thanks to the Steely Dawn Starter Pack you bought
Misty Mountains OR Forochel - 695 TP OR 595 TP
Angmar - 795 TP
Personally I prefer Misty Mountains over Forochel (which is the worst region in the game IMHO), so assuming you go that route you would need a total of 2,680 TP to purchase all four regions. You already have 1,500 TP from your Helm’s Deep and Steely Dawn purchases, so that leaves only 1,180 TP needed. You can earn 915 TP just by doing all available deeds/quests in the FREE regions, leaving 265TP needed to finish your purchases. You can obtain that by either subscribing for one month to activate VIP/Premium status (500 TP awarded), or you can purchase North Downs and do all deeds there and in Evendim (which you own already) to earn more than enough to complete the purchases of the other zones.
My advice would be to wait for one of the fairly frequent sales on regional quest packs that the LOTRO Store runs (they seem to come around every 90 days or so). They discount all regions 20%, which means you only need 2144 TP to snag all the regions I listed above when they are on sale. You’d have 2415 from your purchases and all the FREE region deeds (assuming you’ve completed them all), or if you subbed for a month you’d have 2000 TP from purchases and sub and most likely have easily racked up another 150 TP or so from deeds at that point.
Hope that all makes some sort of sense. Here is a great rundown on the cost of all regions and expansions and how much each region’s deeds return in TP when completed. It provides a framework fro F2P players to essentially grind their way to all content for free, however you’ve already significantly eased this path with your purchases of the Quad Pack, Helm’s Deep and Steely Dawn.