Need help answering questions about transitioning to Win11

For context:

I plan to upgrade to Win11 (by making a fresh install) sometime this or next month, but there are quite a few complicated questions i need to figure out before i do.

I am the tech guy in the family, so i do know how to handle a lot of the PC issues, but hardware and OS stuff arent really my specialty, thus im asking these questions on a forum.

Besides Win10 support ending, another reason why i want to reinstall windows is because i want to finally switch to an SSD from my 11 year old HDD. Why i want to make a fresh install is because i have some garbage on my PC that i cant so simply get rid of. So a clean install would probably be the best option.

Additionally, my motherboard (ASRock Z370M Pro4) Does not have the TPM2.0 which is required to install Win11, but from the information i found it does feature a headder for a TPM chip. So i would also need to buy such chip.

PC specs if relevant:

Mobo - ASRock Z370M Pro4

CPU - I5-8400

RAM - 16GB

GPU - RTX2060

Main questions:

1) What do i need to look out for when buying a TPM chip?

I am unsure about the details about the TPM chips. From what im getting at, Win11 specifically requires TPM 2.0 or better, so im assuming i need to pay attention if the chip im buying supports that version. Whats more important is, are all TPM chips the same? Do they all feature the same connection for the header on the motherboard? Do different motherboards or motherboard manufacturers have different TPM chip models that i need to specifcially look for? I really wouldnt want to spend money on getting a wrong kind of chip that doesnt even help my issue.

I would also appreciate, if someone knows or can figure out if my motherboard (ASRock Z370M Pro4) actually can get a chip required for Win11, or that info about having a TPM headder only refers to an older model that actualy wouldnt be useful for Win11, meaning this whole plan to upgrade to Win11 is a bust.

2) Is UEFI boot mode something special or something that my current installation simply didnt have?

I read somewhere that Win11 also requires Boot mode to be set to UEFI. Curently my Win10 is installed as Legacy boot mode (it was originally installed as Win8 11 years ago). From what i understood, that is something that cannot be changed to a windows that is already installed. Did i undertsand it right, that its simply a setting you choose when installing Windows, and choosing the UEFI should be no issue when installing a fresh Windows (im also assuming Win11 wouldnt even give the choice if it only accepts one option)

3) Can i install Win11 straight away, or do i need to reinstall Win10 first?

Right now i have Win10 installed. I have a Win10 key, and its assigned to my Microsoft account. If i were to install a fresh Win11, could i simply log in with my account that only has Win10, and it would just accept it as the free upgrade to Win 11? Or do i need to install a fresh Win10 and then upgrade it to Win11? Also my OS is Win10Pro, does that mean i would need to get Win11Pro?

4) Is it possible to save/export Windows settings?

It would be convenient if i can somehow export my current Windows settings to that new fresh Win11 install. Is that something possible? Like the windows account saving up some windows settings, or being able to make an exportable file that can be imported into the new install (even if the Windows versions dont match)? This isnt anything major, since if its not possible it would just be a hassle going through all of the many Windows settings that exist nowdays

5) Does Win11 allow for Equalizer enhancement settings?

On Win10 In the sound pannel, choosing the audio device and going to its porperties in the Enhancements tab you can add Equalizer to the audio device. I absolutely need to have this feature, because my current speakers have an awful high pitch sound, i need to tune it down. Why im asking the question if this feature still exists in Win11 is because both my moms and brothers laptops (both running Win11) dont have this feature. So im concerned. is it something that got removed from Win11, or they dont have it because they have laptops, not proper PC towers? This PC has a realtech soundchip on the motherboard, but unlike a much older PC i had, this one does not have an application for realtec sound pannel. So i can handle equalizer-ing only from Windows saund pannel. In the unfortunate case, Win11 doesnt have this feature any more, i would have to find an alternative application that can do it.

6) Does Windows allow to connect multiple drives that use the same letter?

The way i plan to make a fresh install of Windows is by removing my current HDD, install the new SSD. and install Windows on it. Of cource its going to install it as a C: drive. After the installation is complete i would like to reconnect my old drive (which is a C:) to transfer files to the new drives. Because both drives would be C: would Windows have any conflicts and not allow something to function because of that?

7) Is reusing my old HDD a bad idea?

I plan on getting an M.2 SSD probably 500GB or maybe 1TB, but i also want to have a secondary HDD with 1-2TB. Using this PC now i realize 1TB is just not enough for me so i want to have more storage, but i dont want to spend so much on getting an SSD above 1TB, and HDDs in general are cheaper.

The current HDD im using, i have been using for about 11 years. From what i know HDDs livespan is considered to be 5 years. Yet i havent really had any issues with my HDD.

Is it a bad idea to reuse it as that secondary HDD in the new drive layout? Is HDD failure one of those that just come out completely out of nowhere and suddenly stops working without hinting at it beforehand?