The Q9650 is overclockable, but your motherboard needs to have the necessary options in the bios as not all motherboards support overclocking.
I don't think there should be any limiting factors, the 1070 is PCIe 3.0 while your motherboard is more than likely 2.0, but the card is backwards compatible. That said, it'll be great for when you do an upgrade, you can carry the card over.
I'm not too sure on any bad mfg's. EVGA had an issue where cards were catching on fire on their 1070(?)/1080s but that problem has since been fixed, but they have good support. Asus tends to have terrible customer support if there is ever an issue. An example from another forum is someone was on their chat support and had some issue with a component completely dead, Asus' response was literally: "Ok, thanks for contacting us about this! Have a great day!"
A lot of the new cards have a "feature" where if the card isn't working hard, the fans don't spin up until it does something (ie fire up a video game). This is generally dependent on temperatures, however I disabled this (just set the card's fans to spin at all temps) because my friend was having an issue with the card not spinning up while in games, causing some FR drops. I doubt this is a huge problem as I haven't heard too many other instances.