I have a few inter-related ubuntu installation questions.
Note that I have read several forum posts, and installation articles but either they are several years old [and I am unclear if the steps are still accurate], they involve newer UEFI bios', or they describe details which differ from my own installation specifics. Any clarification or guidance on the questions below would be much appreciated.
 Although I would prefer installing what I read is 'long term release' ubuntu 18.04, it doesn't work as well with my convertible laptop, in tablet mode. 19.04 works better, as I have seen when I try out 19.04 off the USB installation medium.
My question is: is it advisable to use 19.04 as a new ubuntu user, who wants to minimize customizing 18.04 in an attempt to achieve a similar tablet mode performance, compared to what I have experienced with 19.04? Any pros and cons specific to this convertible laptop issue?
 I would like to dual boot ubuntu and windows 10 on one 256GB SSD. Via Windows 10, I have already 'shrank' the existing c: drive, to achieve 136GB of unallocated space for the ubuntu installation.
So right now I have the following: 101 GB - windows 10 549 MB - [I believe this is for the windows swap] 136GB - unallocated space for the ubuntu
I have confirmed my BIOS is: Legacy.
Question: I am unclear whether I should, prior to installation of ubuntu, allocate a swap for ubuntu, and also, what the swap size should be? Will the 19.04 ubuntu installation automatically create an appropriate size swap, and prompt me to create one, during the actual installation? I am unsure of what to expect and therefore don't know if I should take action on this ubuntu swap creation detail prior to installation.
I have read rather opposing directions on swap size as well. I have 8 GB of RAM, so doubling it would be 16 GB. Is this the accepted advise or are there various options depending on one's hardware and objectives? Then again, I am a little confused why my Windows 10 OS seems to only have 549MB.
 Disable Fast Startup and Secure Boot. Given that I have a legacy bios, would I turn either, or both, of these startup/ boot options off prior to installation?
What confuses me is, this laptop does boot Win10 quite fast [20 secs] but I thought I read the fast startup was specific to UEFI bios. Note that the laptop originally ran Win7pro, and it was updated to Win10pro if that helps. Ultimately, I would prefer to retain this seemly fast start up speed.
 Would virtualization of the Windows 10 OS, and running it within ubuntu, have advantages? I would consider this solution if there were no additional security disadvantages compared to a dual boot configuration, and, if this was relatively easy to achieve. Any advise on this or experiences to share?
Additionally, I believe there's an option to create a Windows 10 OS on a USB [like linux distributions], but I don't know if this would be difficult to achieve. I am sure others have encountered the same need for both linux and windows, and may be willing to share their experiences.