Ipad plus pencil with Dell laptop

Compatible in what way?

The iPad and Pencil are generally independent of any laptop you use.

You can use the iPad to take notes if that is what you mean, and depending on the app you use you may or may not be able to transfer those notes to the Dell laptop.

If you use for example Microsoft Word to take notes, you can easily transfer the word files to the laptop either via Microsoft's One Drive or using a Usb drive drive.

Outside of that, there's really no direct interaction between the iPad and the Dell laptop. So no real consideration when selecting an iPad and Pencil in regards to that.

Apple has an comparison tool to check the iPads. I would recommend that you get as much storage as you can. Depending on model there is only one pencil to work with a specific model of iPad. Currently there are two models (1st and 2nd generation).

iPad - Compare Models - Apple

Apple Pencil compatibility - Apple Support

You computer can be used to back up your iPad or you can back up to iCloud. Here are some reading on this. Your computer will have to have iTunes installed to do the back up.

What you can do with iCloud storage - Apple Support

How to back up your iPhone, iPad, and iPod touch - Apple Support

There are no specific considerations relating to use with a PC. Your choice of iPad model will principally determined by screen size/technology, TouchID versus FaceID, and performance. When using a PC, you can access iCloud and some synchronised data using a web-browser.

You can directly compare iPad models here:

iPad - Compare Models - Apple

If intending to use an Apple Pencil, be sure to select the correct model. There are two Apple Pencils - first and second generation; they are not interchangeable:

Apple Pencil compatibility - Apple Support

Whatever model of iPad you choose, you would be well advised to purchase as much internal storage as you can afford - as internal storage cannot be changed, upgraded or extended. The available internal storage is fixed for the entire life of the device. If you run out of internal storage for your documents, photos and other data, you will forever struggle and become a source of frustration. It is far better to have more storage than you need, than to need more storage than you have.

A good rule of thumb is to quantify how much data storage you will need - add a healthy margin - then double it. If you are unable to quantify your data storage needs, it becomes more difficult; whilst I cannot make definitive recommendations, personally I would council against purchase of any iPad with any less than 256GB storage - 512GB or greater offering a greater level of safety.  

Within the Apple Support Communities we see regular tales of woe and disappointment when storage requirements are exceeded, necessitating replacement of the device; by contrast, we never see complaint of having too much available storage. It is relatively easy to fill limited internal storage space; perhaps consider higher tiers of storage as providing room for growth as your needs develop or mature - potentially extending the useful usable life of the device. 

Consider also the functional differences between WiFi Only and WiFi+Cellular models of iPad. Only WiFi+Cellular models include GPS capabilities - which may impact any Apps or features that require accurate and consistent location data, such as Mapping. Purchase of a WiFi+Cellular model does not commit you to using Cellular connections, but provides this flexibility should it be needed.  WiFi Only models of iPad have no Cellular or GPS functions at all.

I hope this information and insight proves to be helpful to you.

Other than for using iTunes to sync and transfer data back and forth from PC to iPad and from iPad to PC, photo/image transfers, extended monitor support.and compatibility with online, offsite data storage/back up services.

Not really.

Apps are not cross-compatible in most situations ( with some exceptions ) and the OSes are not compatible.

You CAN certainly use an iPad with your Windows PC, but it is NOT as fully integrated as you seem to be implying.

Since you are a Windows user, why not just look at Surface/Surface Pro tablets which are 100% fully compatible with your Windows PC system.

Best of Luck to You!

If you are fine with what everyone has posted here to date, then, by sll means, purchase an iPad, following all of the other advice given.

Best of Luck to You!