Replacing optical drive with HDD/SSD - tips please

Hi, sorry if this question is posted a lot but I am seeing conflicting information across different sites and I was wondering if anyone could help.

I have a mid-2012 13 inch MBP and I would like to install an SSD as my boot disk, yet keep the internal 750GB HHD in the computer too. To do this I know I must remove the optical drive and I am capable enought to do this, but I have a few questions on the matter:

1) Should I place the SSD in the optical drive slot or is the HDD better in there?

2) With that in mind, is the optical drive area adequately cooled, i.e. would a HDD at 5400rpm be cooled enough not to fail if it were in the opitcal disk space?

3) I know the SSD needs an adaptor like 'Optibay', but will the HDD fit easily in the optical drive space, or will this need an adaptor?

3) Is the optical drive capable of getting the most out of the SSD? i.e. how can I check SATA 2/3 connections in my Mac?

4) After having removed the optical drive, am I correct in assuming all I will need to have a working external disk drive is to use a USB to 13 pin SATA adaptor cable to connect to the laptop?

Thank you in advance! Looking forward to joining the SSD revolution...