Hello,
I don't grow many eulophia species in my collection, mainly because there just not available for sale in the US very often, but I do have two different forms of E. petersii and I have seen a third form in a private collection.
The first photo is of two E. petersii I grow outdoors here, hence the 'rough' shape of the one on the left
. The plants go down to 28F on the coldest days in winter, they are kept bone dry from 2nd week of November through the first week of February and are given supplemental heat from a few strings of Christmas lights for those nights when the temperature would stay below freezing for prolonged periods.
The larger clone grows bulbs up to 25cm in height and foliage that reaches 50cm x 3cm when well grown. The inflorescences grows to 150+cm and branches freely, quite a spectacle when it blooms. I obtained that plant from a specialty nursery here in California and it has been quite easy to care for as it grows with my cymbidiums outdoors.
The smaller clone produces bulbs that reach 15cm in height and the foliage is 25cm x 5cm when well grown. This variety produces an inflorescence that reaches 250+cm in height, tho it does not branch as freely as the first plant (usually only 2 or 3). This was obtained from a succulent society auction table during a fundraiser.
The second photo shows a third variety of E. petersii that is growing in a private collection. The plant in the photo is a division from a large specimen, it is a 'dwarf' variety that usually produces bulbs under 12cm (for the most part) and leaves around 15cm x 2cm in length. The specimen had a few very tall (20 cm) bulbs before it was broken apart but it now remains much smaller in size since being divided. The inflorescence on this reaches 150+cm in height and holds 3 - 5 branches as it develops. I haven't been able to obtain a piece just yet but hopefully soon.
I have seen any other forms of E. petersii as of yet but I am sure there are some intermediate forms and possibly larger forms that are floating around out there. The form you described as having 20cm x 1cm foliage sounds quite interesting, how tall are its bulbs?