Prosody is the science that describes poetry forms called meters or seas (bohor) in Arabic.
The comparison between two prosodies requires some basic knowledge of both prosodies.
In western prosodies there is one form with two analogous but different contents.
Sound and prosodic syllables are represented by U for both unstressed (English) and short (Latin) syllables, which may be represented by no 1.
and _ for stressed (English) and long (Latin), may be represented by 2.
Analogy is best described by Reuven Tsur:
English Renaissance poets thought they succeeded in the adaptation of the quantitative metre. But they were doing something that was very different from what they thought they were doing: working in a stress timed language, they based their metre on the more or less regular alternation of stressed and unstressed syllables, and not as they thought, on the regular alternation of longer and shorter syllables. They used the same names and graphic notation for the various metres, but the system was utterly different, and well- suited to the nature of a stress-timed language
These two symbols 1 and 2 are adequate for linguistic and prosodic rules description of both languages.
When it comes to Arabic these two symbols are adequate only for linguistic description. It falls short from prosodic rules description because Arabic prosodic units are 2 and 3.
3 being a monolithic unit composed of 1+2 (short + long) syllables.
Considering this 3 as one entity is a must to enable a consistent full rule description of Arabic prosody.
Latin is quantitative Arabic is both quantitative and qualitative. Syllable time duration is not the controlling factor.
This long introduction is necessary to answer the other two questions. The answer is descriptive. More explanation is needed for detailed information.
Basic "taf‘īlahs" are two types:
Two units : 2 3 and 3 2
Three units : 2 2 3 – 2 3 2 – 3 2 2
The permutations of these units and (other derived from them) unite in a meter clock which proves that Arabic meters is a manifestation of an arithmetic program felt by Arabs – maybe like other peoples - just like that program felt by bees and controls the design of their cells.

12 is the unit of iambic meters it is a foot . But In Arabic 12 is combined in the monolithic prosodic symbol 3 called watid.
22 is the unit of spondaic meter it is a foot . In Arabic it is considered as two sabab units. less than taf‘īlah
So generally we can say a Latin foot ranges between the Arabic watid 3 and the taf‘īlah
Relevant subjects: Is there a poetry in architecture?
I hope you find the answer useful.

This youtube video provides a clear example. It can be understood in English, Arabic and its original Sanskrit.
Please listen to the first half line (00:19 - 00:23) in this song. Its pronunciation is "Fee layaalin katamat sirral hawaa". Word meanings are:
- Fee = in = في
- Layaalin = nights = ليالٍ
- Katamat = concealed = كتمت
- Sir = secret = سرّ
- Alhawa = love = الهوى
Cv = da = 1 & CV = Cvv = CvC = DUM = 2
Scansion: Fee layaalin katamat sirral hawaa
- Fee =CV=2
- Layaa=CvCV=12=3
- Lin=CvC=2
- Ka=Cv=1
- Tamat=CvCvC=112=13
- Sir=CvC=2
- Ral=CvC=2
- Hawaa=CvCV=12=3
Bid=2 Dojaa=3 Law=2 Laa=2 Shomoo=3 Sol=2 Go=1 Raree=3. Pattern is: 2 3 2 1 3 2 2 3.
Further details and many lines are explained on The Poetry Free-for-all; threads #11 and #12; unfortunately most of the links there are no more active.