What stylus is compatible with ipad mini 2 A1489 for note taking? Or how best can I hand write notes onto Word & PDF doc's using either the iPad mini 2 or my Macbook Pro 13 (2020)

Your iPad mini2 fundamentally doesn't support Apple Pencil.

Third-party Bluetooth stylii, such as Adonit, are entirely reliant upon support being explicitly provided by Apps. As such, you are unlikely to find Apps that are (a) compatible with your very old-model iPad (that itself cannot be updated beyond iOS 12.5.7 - iPadOS 17.7/18.0.1 being current) - and (b) provides support for a specific Bluetooth Stylus.

Your remaining option is to use a passive capacitive stylus - these being readily available. However, this type of stylus has no more functionality or capability than your fingertip - although those with a fine tip may offer slightly more accurate screen positioning.

Given your stated goal (i.e., your "mission"), you might be best advised to consider replacing your elderly iPad mini with a much newer or current model iPad that supports Apple Pencil...

There are four models of Apple Pencil - each being compatible with a limited range of iPad models. Here is Apple definitive compatibility list - and comparison chart:

Apple Pencil compatibility - Apple Support

Select Apple Pencil - Apple

You're very welcome.

The benefit of replacing your iPad with a current model will be profound...

1) You will not only have benefit of a modern Operating System (iPadOS 18.x) and its much newer capabilities and features, but will also remove the issue of current Apps not be available or compatible with your current iPad.

2) Apple Pencil support, being implemented by the OS and not by explicitly by Apps, provides near universal ability to use the Pencil. Some Apps take Apple support even further, offering additional functionality. Unlike iOS, recent versions of iPadOS also offer handwriting recognition - either transcribing handwritten input to standard text - or simply improving untidy scrawl to something much more readable.

Frankly I'm not sure any stylus is going to be truly effective with that iPad. But the Adonit stylus models are available from Amazon UK if you want to look into one and give it a try:

https://www.amazon.co.uk/s?k=adonit&ref=nb_sb_noss

I don't use any stylus myself so I can't comment as to how well any work, nor whether Microsoft Word or any PDF editor will support a stylus on your device.

Regards.

All iPad models have broadly the same core capabilities. Models essentially differ in their ultimate performance and physical attributes. iPad Pro models use FaceID for biometric user-authentication, while others use TouchID.

You can compare iPad models here:

iPad - Compare Models - Apple

When choosing an iPad, don't forget to consider the relative benefits of the different Pencils. The Apple Pencil Pro and the second generation Apple Pencil are paired/charged wirelessly simply by attaching the Pencil to the magnetic/inductive charging port of the host iPad. By comparison, the first generation Pencil and low cost USB-C Pencil rely upon a wired connection. Beyond the compatibility list already provided, Pencils are not interchangeable between iPad models.

Whichever iPad model you ultimately choose, you would be well advised to purchase as much internal storage as your budget might reasonably allow - as internal storage (and other hardware) 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 and others cannot make definitive recommendations for your personal needs, objectively I would council against purchase of any iPad with any less than 256GB storage, 512GB and higher having a greater margin for growth.

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. 

Also consider the functional differences between WiFi Only and WiFi+Cellular models of iPad. Aside from the obvious Cellular functionality, only WiFi+Cellular models include GNSS/GPS location capabilities - which may impact any Apps or features that require accurate and consistent location data, such as Mapping. 

Purchase of a WiFi+Cellular model provides access to precise location services, but does not commit you to using Cellular connections. WiFi Only models of iPad have no Cellular or GNSS/GPS functions at all.

You are very welcome.

If you need any additional advice or guidance, don't hesitate to ask. There are many senior members here with a wealth of knowledge and expertise. It's much better to ask before making a substantial outlay in a new purchase.