Understanding Intel I5 and I7 processors

[TeaMan]

I am in need of a new laptop and trying to decide if I want an I5 or I7 processor. If my memory serves me, I remember the I5 being 2 cores and more useful to someone that doesn't have high end applications that use multiple cores and the I7 was a quad core and geared for high end users that have programs that use multiple cores. I don't game, and use graphics programs like Autocad occasionally. My seem to remember running a program that isn't built to use multiple cores on a quad core processor such as an I7 would actually run slower because it would run on only one core and at approximately 1/4 the speed of the multi core processor.

Can anyone lend me some knowledge on this? It's been too long away from computer specs for me to keep it straight anymore.

Thanks, Much appreciated.
TeaMan

[GObonzo]

it depends on the actual processor, not just if it's i5 or i7 or even i9.
there are many versions of each, some 4 core, some 6 core, some 8 core, etc.
some of each type with low clockspeed and less cache available, some with higher clockspeed and other greater benefits available.

you would need to specify exactly which processor the laptops you are checking out had to get any type of comparison between them.

[TeaMan]

I've been away for a bit. I have some more information that could help this discussion. I don't game with my laptop and battery life is important. It used to be true that I7 processors that had multiple cores required software that could access all the cores. Software that couldn't would only use one core and run significantly slower. My software may not use more than 1 core, so I want to get the right processor to do the job for me.

The two processors that seem to come up most are the 9th generation Coffee Lake I5-9300H (2.4 GHZ - 4.10 GHZ, 4 core, 8 thread)45W, and the 9th generation Coffee Lake I7-9750H (2.6 GHZ - 4.5 GHZ, 6 core, 12 thread)45W. I'm looking for the right processor to do things like Autocad 2015, microsoft office applications, internet research etc.

Hopefully this is enough to be able to narrow things down.

I have an additional question about SSD drives. There seem to be quite a few differences in cost there too. I'm going from platter drives to SSD, but 1TB SSD isn't out of the question which would be all I'd need. Most configurations will do either two SSD's or an SSD and platter type drive. Any recommendations there also? What I see are access speeds which are:
2000mb/s Read 1750mb/s write
3500mb/s Read 2700mb/s write
5000mb/s Read 4400mb/s write

Is it worth the upgrade to the faster speeds for the way I use my laptop?

Thanks in advance for the help.
TeaMan