These kinds of discussions can only really take place when we actually have personal realizations. Just quoting and throwing out quotes will not do. There must be personal realizations otherwise there can be no real discussion. It will not be fruitful. After all the purpose of discussing Krishna is to attract the Lord. "Oh, they are talking about Me?" It is like an offering of food stuff. We prepare something nice to offer to Krishna for His eating pleasure. When discussing Krishna it is like that. It is for His pleasure. Not as a battle for who is the "winner."
Recently a devotee posted that his understanding is that the Virata Universal Form is real and that this is supported in the Rig Veda. So I had to dig a little deeper how to reconcile that the Universal Form could be real and imaginary at the same time.
My understanding is that the Universal Form is not a Vishnu Form and is not eternal. This is explained by Srila Prabhupada in several places. Therefor it is referred to as imaginary. We know that it is only manifest as long as the material universe is manifest. Srila Prabhupada says It has nothing to do with the spiritual world or the internal energy of the Lord.
If we consider the benefit to those who meditate on the Universal Form we see it is helpful for developing Krishna consciousness just like the things of this world can be helpful if they are seen in relationship to devotional service. A car is not eternal and really has nothing to do with the spiritual world. but if it is used in Krishna's service rather than for joy riding the devotee becomes purified. The universal form is not eternal but it can be useful for philosophers to meditate on it and in that sense it could be said to act like a vehicle bringing the meditator closer to appreciating the magnificence of the Lord.
"...the kingdom of God, which is sanatana or eternal and is therefore not exactly like the material creations described above. The virata universal form of the Lord is an imagination for the material world. It has nothing to do with the spiritual world, or the kingdom of God." SB 2.5.39 purport.
It can be considered real in the same way anything which is temporary in the material world is considered "real."
Krishna reveals His universal Form to Arjuna to reassure him that He is indeed the Lord of the universe and as the devotee pointed out anyone claiming to be God must be able to show their Universal Form. So yes the Universal Form is real but it is temporary so it is also imaginary.