Windows 10 Upgrade or Fresh Install for 7 Pro Desktop

Hello, due to a variety of reasons, I am a long-time user of a 64 bit Windows 7 Pro SP1 desktop who has made no plans for its impending end of support.  I am looking for advice on the best way to transition to Windows 10 - upgrade or fresh install.

My computer is a custom built desktop that I am very happy with and do not want to replace.  I have many applications installed, some of them are older and I am afraid I will lose them in the transition...

I am not sure what info you will need to help with the decision, but here are some key specs on the desktop:

•    Motherboard: ASUS P8Z77-V LK LGA 1155 Intel Z77
•    CPU: i7-3770K 3.5 GHz
•    RAM: 16 GB (can expand if needed)
•    Graphics Card: NVIDIA GeForce GTX 460 V2 1GB 192-bit GDDR5 PCI Express 2
•    Monitors: two 24" LED monitors
•    Boot drive: Samsung 850 Pro 512GB SSD
•    Other internal SSD: Samsung 840 Pro 256GB SSD
•    Other Internal HDDs:  Multiple Western DIgital HDDs (2TB and 8TB)
•    Network: Member of server-based Workgroup
•    Server: Dell Power Edge 110 II running Windows Server 2012 R2 Essentials (manage server using Remote Desktop from W7 PC)

If the best path is to update my boot drive, it currently has only 57GB free.  There are a lot of pictures and videos I can move off it to free up 200+GB of space.  I am more than happy to purchase a new SSD for a clean install of W10 if that is the better way.  I have plenty of open slots or I may simply replace the existing 256GB SSD.

Is it possible to have a second SSD boot drive for Windows 10 and keep my existing drive so if I run into application issues I can boot off the old W7 SSD when needed?

I want to make the transition over the next 10 to 15 days, but would like to buy any required hw/sw before the end of the year.  I know I need a W10 Pro license ($200) and possibly a new SSD and maybe a RAM boost to 32GB?

I am going to start the process of checking and updating the firmware and bios on all my devices - something I have not done in a while.

Thanks for your help!

P.S. I have a W10 2-1 laptop I just purchased and can use when I need features like a touch screen. I can say I want to make sure One Drive is disabled on my desktop.  It would be nice to add a fingerprint reader for sign on if that is easy to do.  Touch screen abilities can wait for now - but I would be interested to know how I can add it in the future.

PPS. Update - I was pulled away on some family matters but no plan to resolve this in the next 5-7 days.