RAM upgrade slow boot

Much much better. I don't see any of the usual software suspects. You're running a fusion drive with a 7200 rpm drive which is better than some that have a 5400 rpm drive and those are glacially. slow.

You have a number of items in the User Login section. I would remove them from the login pane an test to see if there's any improvement.

Here's some food for thought: unless you're using a true VPN tunnel, such as between you and your employer, school or bank's servers, they are questionable from a privacy standpoint.  Read these two articles: Public VPN's are anything but private and Former Malware Distributor Kape Technologies Now Owns ExpressVPN, CyberGhost, Private Internet Access, Zenmate, and a Collection of VPN “Review” Websites. 

I notices that NordVPN IKE has a number of helper files running. . I'd uninstall it according to the developer;s instructions and test to see if that improves boot speed, etc. If it's needed for work, school or banking you can reinstall it.

Also, Addressbookmanager is taking up 34% of you CPU. There's sometime amiss there. That may be you bottleneck there. Give the fix in this user tip a try: Fix corrupted Contacts database - Apple CommunityOfficial Apple Support Community. I'd give this a try first.

It requires erasing the drive I think, but...

If your Mac has a Fusion Drive and you see a flashing question mark or alert, see the troubleshooting section of the Apple Support article About Fusion Drive, a storage option for some Mac computers.

If you continue to have problems with your disk or it can’t be repaired, it may be physically damaged and need to be replaced. For information about servicing your Mac, see Find out how to service or repair your Mac.

In Terminal…

diskutil resetFusion

Where did you get the Crucial RAM from? If from Crucial directly I would not think it would be a problem. However, if you got it there a 3rd party vendor like eBay or Amazon then you might be getting those that scored lowest on the compatibility texts. And we know that Macs are extremely sensitive to the quality of RAM. And RAM is not a major contributor to slow booting. That's the hard drive speed and some software (but it usually affects performance instead of boot speed).

Boot into Safe Mode according to How to use safe mode on your Mac and measure the boot speed. All 3rd party software is prevented from launching under Safe Mode so that should tell us if it's software that's the culprit.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

A1419 covers Mac from Late 2012 to Mid 2017...

Lookup Mac Specs By Serial Number, Order, Model & EMC Number, Model ID @ EveryMac.com

Which exact Mac do you have. Apple logo at top left>About this Mac…

We need to see what all is running, a report from this will not display any personal info...

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info.

https://www.etrecheck.com/

Pastebin is a good place to paste the whole report if you capture the URL while there…

Workable but harder for me to work with...the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck. In a Reply before you click post, look for this to add longer texts...

Please rerun Etrecheck and add the report according to the following:

Copy the report

and use the Additional Text button to paste the report in your reply.

The way to copied the report and added it gives this which is near impossible to read:

Hardware Information:

    iMac (Retina 5K, 27-inch, 2017)

        Status: Supported

    iMac Model: iMac18,3

    3.4 GHz Quad-Core Intel Core i5 (i5-7500) CPU: 4-core

    40 GB RAM - Upgradeable

        BANK 0/DIMM0 - 16 GB DDR4 SO-DIMM 2400

        BANK 0/DIMM1 - 4 GB DDR4 SO-DIMM 2400

        BANK 1/DIMM0 - 16 GB DDR4 SO-DIMM 2400

        BANK 1/DIMM1 - 4 GB DDR4 SO-DIMM 2400

It would appear that the 2x16GB RAM that you recently purchased either 1) does not match the specs required by your 2017 iMac, 2) has specs that are different from your 2x4GB RAM or 3) is bad.

Please tell use the exact model iMac you have. Also, with the original 2x4GB RAM in the iMac, go to Apple > About This Mac and tell us the details it says for Memory. And if you have the information, what are the specs on the 2x16GB RAM that you purchased (for example, PC4-19200 DDR4 SDRAM SO-DIMM (260-pin), 2400 MHz.)

Can't swear to it, but it looks like your Fusion drive is split, did you erase &reinstall recently?

Do you have a good backup or two?