If it were God,the Father,and the Holy Spirit,it would have to be a visible manifestation of them,which they would have to create human bodies for themselves,but it is not them,for Christ is the last human form that God will show on earth,and when Christ returns He will have a glorified body,and has a glorified body now.
Zec 4:11 Then answered I, and said unto him, What are these two olive trees upon the right side of the candlestick and upon the left side thereof?
Zec 4:12 And I answered again, and said unto him, What be these two olive branches which through the two golden pipes empty the golden oil out of themselves?
Zec 4:13 And he answered me and said, Knowest thou not what these be? And I said, No, my lord.
Zec 4:14 Then said he, These are the two anointed ones, that stand by the Lord of the whole earth.
Rev 11:3 And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth.
Rev 11:4 These are the two olive trees, and the two candlesticks standing before the God of the earth.
Also we see it is not God,the Father,and the Holy Spirit,for they are the two olive trees,and the two candlesticks standing before the God of the earth,so the two witnesses,are separate from God,the Father,and the Holy Spirit,although they are led by the Holy Spirit.
Jesus did many wonderful works on earth,which no individual person can duplicate,but Jesus said the saints will do greater works than Him,because He goes to the Father,which means collectively they will impact more people,for they will impact the world,where Jesus impacted Israel,but it is all done by the leading of the Spirit.
Jesus said that if you seen Him,you seen the Father,and it is the Father that dwells in Him,He does the works.
Jesus said the kingdom of God is within you,which means if you are led of the Spirit,you will show the kingdom of God's ways upon earth.
A saint that is led of the Spirit,will do the same things,impact things in the same way,have an influence upon people,the same way Jesus did,and it will be God in them doing the works,and God's ways being shown through them,the kingdom of God.
So God,the Father,and the Holy Spirit,do not need to prepare bodies for themselves,to be the two witnesses,because any saint that is led of the Spirit,is God doing work through them,just the same as if God prepared a body for Himself,and witnessed to them,so God could use them,and work through them to witness,which would be the same as if Jesus did it,God manifest in the flesh.
But of course this is if the person is led of the Spirit,and we can falter from time to time,and sometimes might not allow God to work though us,because we want to dabble in sin a tad bit,and might waver because of persecution,and not be bold like we should,in other words we can allow the Spirit to lead us,and we will act like Christ,but being we are not with Christ yet,the flesh can still cause us from time to time,not allow the Spirit to lead us,if we allow that to happen.
But the two witnesses will not have that problem,for they are already standing before the God of the earth,so they cannot falter,and cannot fail,and cannot do their own will,but only the Father's will,for they do not have the choice to rebel,for they already made the choice beforehand to be with God.
I do not believe they are angels,for God does not use angels in flesh to promote His kingdom,and witness about it,but He uses people,because the Church consists of people,so they would have to be people,and they cannot be people born before they witness,being a young age when they witness,for the two witnesses stand before God that is not on this earth.
Some people think it is Moses,and Elijah,but if it is two people,they would have be very influential,and important people,in the Bible,pertaining to the will of God,which those 2 would fit that description,and both of them was with Jesus,when He transfigured Himself,which the disciples saw.
God,the Father,and the Holy Spirit,will not be the two witnesses,and it would not be angels,for the church consists of people,so He will use people to witness concerning His Church,and they cannot be born on earth around this time,because they are standing before the God of the earth,so it has to be two people that are part of God's kingdom right now,being with Him,and not on this earth right now.