I am using Note 10+ currently.

I attend quite a number of talks/ training and take notes frequently.

For me, Note 10+ screen size is small for note taking. However Note 10+ is great for writing small notes.

I am thinking to get Tab A with S Pen to use it with my Note 10+(easy for S Notes syncing)

Question: Is Samsung Tab A(latest one) reliable and good? Is the Tab A camera good quality?(as sometimes I will use it to take pictures during the talks)

I advice you to go to the shop to try it out yourself.
Also you are aware the Tab A specs are mid-range right, and the price is consider "cheap" for Samsung's tablets.
If you don't mind spending more, you can get a more decent tablet which is the latest Tab S it has a stylus but big in size.

Since you will be attending quite a number of talks / training and will take down notes frequently, I suggest you to get the Samsung Galaxy Tab S6 as it is the latest one and are able to goes beyond boundaries with whole new levels of S Pen integration, for both work and play. Now your S Pen is always by your side. A subtle indent on the back magnetically attaches it to the rear of your Galaxy Tab S6, so you're always ready to jot down and retain your ideas. The S Pen automatically starts charging the moment you attach it.

crazy expensive this model

Yes, you should get the tab a with s pen. 8 inch should be ideal for writing notes.

I think the camera is ok but it doesn't have flash. If you want a powerful tablet, get the latest tab s6.