Let's me give you a perspective of what you can expect from this router, or others in the same range: ADSL and VDSL are no problem at all, it handles SQM fine with not a lot of CPU overhead (tested on a 50 mbit VDSL line). OpenVPN client and server are not a problem either, however, expect the CPU to max out at about 15 mbit.
I don't have hands-on experience with Adblock, but I can see RAM being an issue there, what with handling the lists and huge amounts of iptable rules (someone CMIIW). 64 MB are not horribly tight for everyday operation, but don't leave much room for memory-intensive tasks.
For that same reason, I am pretty sure you won't have a lot of fun using this router (or indeed, any small to mid range device) as a download manager. I would recommend getting an external NAS or NAS-like device for that.
OpenWrt/LEDE does not offer any facility for that, neither do any packages.
i know its very basic but you can ask for any missing details and i will add
btw if the router didnt hold the vpn i will use my old pc for vpn and add it between the main dsl router and the wired lan devices.
it will contain but in case it cant hold it because of the limited processing power i will use my old pc.
in that diagram the router should have vpn inside it.
If you want VDSL in a modem form don't bother with the NetGear modem, it's rubbish, look on ebay for a HG612, proper bridge mode modem with a Broadcom SoC (which is generally superior to Lantiq and Mediatek for VDSL)