The Brigade was most often equipped with 75 mm artillery. The 150s were usually Divisional Support Artillery because of their lower mobility and heavier needs for logistical support and transportation. In the Division video, it's pointed out the artillery at the lower level was 75s. Machineguns and low level AT rifles were/are part of the infantry. From the Wiki:
Improved Infantry Equipment 1: Personal and crew served weapons for infantry as well as the various other bits of kit a soldier needs. Improved weapon models and more specialized equipment.
Infantry Equipment II: Personal and crew served weapons for infantry as well as the various other bits of kit a soldier needs. Modernized to include a great number of sub-machineguns and anti-tank rifles.
Infantry Anti-Tank I: Arming our infantry with anti-tank rifles will allow them to take out lighter armored vehicles while maintaining mobility.
Infantry Equipment III: Personal and crew served weapons for infantry as well as the various other bits of kit a soldier needs. Further modernized to include personal Assault Rifles and anti-tank rockets.
And the list goes on. That's where the infantry support weapons are.
While this is true, the regimental infantry guns were 6x 75 mm and 2x 150mm IG 18, in the 13th company of the regiment.
Note that they are not in the battalions TO&E, but the regiment's/brigade's.
So, organizational and equipment wise, they would actually form a 9 battery Battalion of direkt fire artillery. Well, 9 batteries? That's three battalions! A bleeding regiment!!
Would justify 6 ART, with 2 AT and 9 INF for a German division.
Makes 38w, 13000 men + 2500 in support for 15500, which quite nicely is the about combat troops number of a 1st Wave German infantry division.
On a side note, I cannot help but note that the "historical" side in this Argument is perfectly fine with abstraction as long as the Battalion count is what they consider accurate, but balk at the very prospect of abstracting from organization to achieve correct number of guns/men.
Not to mention that missing horses, small vehicles and light trucks, regimental recon platoons, regimental field medics, or even entirely misplaced artillery regiments (!) are obviously "historical".
I can fully accept a certain perspective on what any person would find important for historicity, but plain statements like "40w is unhistoric/only realistic size is 27w/abstraction is good if it works in favour of my position" are extremely weak discussion style.
Furthermore, the wiki says that infantry Equipment is personal or crewed weapons, but fails to Point out what this is.
50mm mortars? Yes, very likely so. LMG? Probably as well. 81mm mortars? I would not object.
A 75mm gun in a company directly subordinate to a higher Echelon? That's not infantry equipment - because it does not belong in the infantry battalion!
The regimental AT guns are, for the very same reason, NOT infantry equipment. The AT rifles are, but there's 36 guns in the Division that are not part of infantry battalions.